MACHINE  SHOP  WOKK 


COMPREHENSIVE    MANUAL    OF    APPROVED    SHOP     METHODS 
INCLUDING  THE  CONSTRUCTION  AND  USE  OF  TOOLS  AND 
MACHINES,  THE  DETAILS  OF  THEIR  EFFICIENT 
OPERATION,  AND  A  DISCUSSION  OF  MOD- 
ERN PRODUCTION  METHODS 


BY 

FREDERICK  W.  TURNER 

HEAD,    DEPARTMENT   OF    PATTERN    MAKING,    MECHANIC 
ARTS   HIGH    SCHOOL,    BOSTON 

AND 

OSCAR  E.  PERRIGO,  M.  E. 

CONSULTING  MECHANICAL  ENGINEER 

EXPERT  PATENT  ATTORNEY 

AMERICAN  SOCIETY  OF  MECHANICAL  ENGINEERS 

AUTHOR  OF  "MODERN  MACHINE-SHOP  CONSTRUCTION, 

EQUIPMENT,  AND  MANAGEMENT*',  "LATHE  DESIGN, 

CONSTRUCTION,  OPERATION*',  ETC. 

AND 

HOWARD  P.  FAIRFIELD 

ASSISTANT    PROFESSOR  OF  MACHINE    CONSTRUCTION, 

WORCESTER   POLYTECHNIC   INSTITUTE 
AMERICAN    SOCIETY    OF    MECHANICAL    ENGINEERS 


ILLUSTRATED 


AMERICAN  TECHNICAL  SOCIETY 

CHICAGO 

1919 


COPYRIGHT,    1916,  1918,    BT 

AMERICAN   TECHNICAL   SOCIETY 


COPYRIGHTED    IN    GREAT   BRITAIN 
ALL   RIGHTS    RESERVED 


INTRODUCTION 

TV  /IARVELOUS  accomplishments  in  the  mechanical  world  have 
AVI  become  so  common  in  this  day  and  age  that  we  scarcely 
realize  the  slow  process  of  evolution  which  machine  shop  work  has 
been  undergoing  during  the  last  century.  Barely  a  hundred  years 
ago  Watt,  the  father  of  the  steam  engine,  had  to  be  satisfied  with 
engine  cylinders  which  were  three-eighths  of  an  inch  out  of  true 
because  neither  the  machines  nor  the  workmen  could  do  better. 
Our  present  day  machinist,  on  the  other  hand,  must  make  his 
error  two  hundred  times  as  small  to  meet  the  requirements.  He 
also  must  deal  with  machines  and  mechanical  problems  which 
would  have  staggered  his  untried  and  unskilled  brother  of  the 
previous  century. 

9  And  it  is  not  only  the  workman  who  has  progressed  in  accuracy. 
There  are  myriads  of  machines  which  have  been  built  to  facilitate 
the  manufacture  of  all  parts  that  go  to  make  up  a  mechanical 
device — speed  lathes,  milling  and  stamping  machines,  die  presses, 
and  the  jigs,  tools,  and  dies  which  go  with  them — and  all  of  these 
contribute  mightily  to  the  accuracy  and  speed  of  manufacture. 
One  of  our  best  known  automobiles  is  made  with  such  precision 
from  radiator  cap  to  differential  that  the  parts  are  shipped  "knocked 
down"  to  distant  points  and  are  assembled  with  practically  no 
fitting — a  truly  marvelous  performance  and  one  which  necessitates 
an  exactness  in  the  duplication  of  parts  which  would  have  been 
impossible  even  ten  years  ago. 

<I  The  tale  of  this  development  of  machine  shop  work  is  an  inter- 
esting one  and  should  appeal  not  only  to  the  technically  trained 
man  who  desires  the  best  advice  on  the  correct  mechanical  process 
to  follow,  but  also  to  the  man  who  wants  to  know  how  to  "do 
things"  or  at  least  how  things  are  done.  It  is  the  hope  of  the 
publishers  that  this  book  will  satisfy  a  real  demand  and  prove 
of  sterling  value  in  its  field. 


VIEW  OF  BECKER  CONTINUOUS  MILLER  MILLING  CONNECTING-ROD  FIXTURE 

Courtesy  of  Becker  Milling  Machine  Company,  Hyde  Park,  Massachusetts 


CONTENTS 


HAND-OPERATED  TOOLS 

PAGE 

Measuring  tools • 1 

Angular  measurement. 1 

Linear  measurement 7 

Hand  equipment 22 

Hammers -. 25 

Chisels 4 25 

Files 29 

Hand  punches 36 

Reamers 43 

Taps 47 

Threading  dies 50 

POWER-DRIVEN  TOOLS 

Lathes 53 

Speed  lathes 53 

Tools  for  hand  turning 54 

Engine  lathes '. 56 

;  Chucks 67 

Mandrels 69 

Cutting  tools 71 

Mounting  work  on  lathe 83 

Turning 88 

Screw  cutting 98 

Drillers : . .  . .  109 

Sensitive  driller 110 

Power  feed  driller Ill 

Multiple  spindles 113 

Radial  driller 113 

Planers 118 

Planer  tools 121 

Plate  planer 125 


CONTENTS 

PAGE 

Shapers 126 

Types , 126 

Blotter 128 

Milling  machines 131 

Simple  milling  operations 131 

Milling  cutters 133 

Types  of  milling  machines 146 

Spirals 165 

Cams 166 

Gears 168 

Grinding  machines 171 

Value  of  grinding  as  finishing  process 171 

Features  of  grinding  process 172 

Laying  out  work 178 

Cutting  round  bars 178 

General  suggestions 181 

Shop  suggestions ,, 182 

Peening 182 

Drilling  hard  metals 183 

Generating  surface  plates 184 

Lining  shafting 188 

Machine  setting 189 

Gear  cutting 193 

Theory  of  tooth  gearing 193 

Designing  gears 196 

Milling  process 214 

Planing  process 216 

General  conditions  of  practical  gear  cutting 218 

Typical  gear-cutting  machines 222 

Turret  lathes 229 

Turret-lathe  tools 239 

Turret-lathe  operations 244 

Automatic  screw  machines 250 

Types 251 

MODERN  MANUFACTURING 

Production  methods 266 

Single  purpose  machines 266 

Selling  costs .269 


CONTENTS 

PAGK 

Grinding  machines 270 

Cylindrical  grinding 271 

Wheels 271 

Grinding  methods.  . 274 

Milling  machines 285 

Types.. 285 

Production  cutters 286 

Cutting  speeds 287 

Drilling  machines 290 

Heavy  high-speed  drillers 290 

Light  high-speed  drillers 291 

Production  figures 292 

Turning  machines 296 

Turning  lathe * 296 

Automatics 303 

Planing  machines 306 

Production  planers 306 

Work  holding 307 

Broaching  machines 309 

Types  and  nature  of  work 309 

Production 310 

Production  tools,  jigs,  and  fixtures 314 

Cutting  tools 314 

Jig  design  and  construction 319 

Tolerances 329 

Guide  bushings 330 

Fixtures 333 

Ball  bearings 335 

Load  capacities 336 

Magnetic  chucks 339 

Uses  in  production  work 339 

Safety  first .343 

Safety  devices  on  machines 343 

Means  of  safeguarding 344 


MACHINE  SHOP  WORK 

PART  I 


HAND=OPERATED  TOOLS 

Simultaneous  Use  of  Hand  Tools  and  Machines.  Machine 
shop  work  is  usually  understood  to  include  all  cold  metal  work  in 
which  a  portion  of  the  metal  is  removed  to  make  the  piece  of  the 
required  shape  and  size  either  by  power-driven  or  hand  tools.  How- 
ever, there  are  some  branches  of  cold  metal  work,  such  as  sheet- 
iron  work  and  coppersmithing,  that  are  not  usually  included  in 
machine  shop  work. 

As  the  hand-operated  tools  are  much  simpler,  and  as  the  opera- 
tions performed  with  them  are  in  every  case  more  typical,  their 
description  and  use  should  precede  that  of  power-driven  tools.  It 
should  be  clearly  understood,  however,  that  machine  shop  practice 
involves  the  use  of  both  classes  at  the  same  time.  Even  hand 
tools  are  not  used  in  the  same  order  on  different  classes  of  work; 
it  is,  therefore,  impossible  to  describe  them  in  the  order  of  use. 
Simplicity  of  construction  and  operation  will  be  the  guide  for  treat- 
ment in  the  following  pages. 

MEASURING  TOOLS 
ANGULAR  MEASUREMENT 

Surface  Gage.  The  surface  gage  is  used  in  laying  out  work 
for  the  bench,  lathe,  or  planer.  The  ordinary  form  consists  of  a 
heavy  base,  an  upright  which  is  firmly  attached  to  the  base,  and  a 
scriber  or  scratch  awl.  In  the  universal  gage,  the  upright  is  pivoted 
at  the  base  so  that  it  may  be  used  at  any  angle.  In  some  forms 
the  base  is  grooved  in  order  that  the  gage  may  be  used  on  cylindrical 
work  as  well  as  on  flat  surfaces,  Fig.  1. 

To  use  the  gage,  the  part  of  the  work  to  be  laid  out  must  be 
prepared  so  that  lines  drawn  on  the  surface  will  show  distinctly. 
A  rough  or  unfinished  surface  is  covered  with  chalk,  a  finished  or 
bright  surface  should  be  copper-plated  by  applying  a  thin  coating 


2  MACHINE  SHOP  WORK 

of  copper  sulphate  solution-  with-  0  brush  or  a  piece  of  waste.  In 
use,  the  work  and  the  gage  are  then  placed  on  a  true  surface  and  the 
scriber  adjusted  to  the  desired  height.  The  lines  are  drawn  by 
moving  the  surface  gage  along  on  the  true  surface,  keeping  the  point 
in  contact  with  the  work.  After  scribing  the  lines,  it  is  well  to 
place  light  prickpunch  marks  at  frequent  intervals  along  the  lines, 


Fig.  1.     Universal  Surface  Gage 
Courtesy  of  the  L.  S.  Starrett  Company,  Athol,  Massachusetts 

so  that  the  position  may  be  located  if  the  chalk  or  copper  sulphate 
becomes  effaced. 

Straightedge.  The  straightedge  consists,  in  its  simplest  form, 
of  a  thin  flat  piece  of  steel,  often  unhardened,  with  accurately 
finished  straightedges.  The  very  small  sizes  used  in  fine  work  are 
occasionally  made  with  a  hardened  knife  edge.  A  non-conducting 
handle  is  sometimes  used  with  the  small  sizes  to  prevent  distortion 
from  the  unequal  heating  due  to  handling.  The  short  lengths 
used  for  ordinary  shop  purposes  have  one  edge  beveled  and  are 


MACHINE  SHOP  WORK 


thick  enough  to  avoid  bending,  Fig.  2.    The  larger  sizes,  from  3 

to  10  feet  or  more  in  length,  are  usually  made  of  cast  iron  with 

one  .finished  edge.    The  metal 

is  so  distributed  as  to  combine 

lightness  with  great  rigidity,  the 

tendency  of  the  ends  to  drop 

being  resisted  by  the  truss-like 

form  of  the  casting  shown  in 

Fig.  3.     The  flat  form  is  used, 

in  connection  with  the  scriber, 

to  draw  accurate  straight  lines 

,  ,,  A  „          ,  Fig.  2.     Steel  Straightedge 

on  plane  surfaces.     All  styles  are 

used  to  test  the  truth  of  plane  surfaces  by  placing  the  straightedge  on 

the  surface  to  be  tested  in  not  less  than  the  six  positions  shown  in  Fig.  4. 


o 


o 


o 


o 


Fig.  3.     Cast-Iron  Straightedge 


Keyseat   Rule.     For   drawing  lines  and  laying  off  distances 
on  curved  surfaces,  such  as  shafts,  a  combination  of  two  straight- 


Fig.  4.     Diagram  Illustrating  Use  of  Straightedge 

edges,  or  a  straightedge  and  a  rule,  is  used.    This  is  often  called 
a  keyseat  rule  because  its  chief  use  is  laying  out  keysways  on  shafts. 


4:  MACHINE  SHOP  WORK 

However,  many  machinists  call  it  a  box  rule.  It  is  usually  made 
in  one  piece,  although  some  manufacturers  provide  clamps  by  which 
the  two  separate  pieces  are  held  at  right  angles  to  one  another. 


THE  LS.  STARRETT  CO 
ATHOL.MASS.U.SA 


Fig.  5.     Keyseat  Rule 
Courtesy  of  L.  S.  Starrett  Company,  Athol,  Massachusetts 

A  more  simple  combination  is  shown  in  Fig.  5,  the  second  scale 
being  represented  by  two  special  clamps. 

Flat  Square.  The  simplest  form  of  square,  called  the  flat  square, 
Fig.  6,  is  a  combination  of  two  straightedges  at  right  angles.  This 
is  a  useful  form  where  the  square  is  laid  on  the  work.  One  blade 
is  usually  graduated  on  the  inner  edge,  and  the  other  on  the 
outer  edge. 

Try  Square.  The  try  square,  Fig.  7,  consists  of  a  beam  and 
a  blade  at  right  angles.  The  beam  is  much  thicker  than  the  blade 


Fig.  6.     Thin  Steel  Squares 
Courtesy  of  L.  S.  Starrett  Company,  Athol,  Massachusetts 

and  somewhat  shorter.  Try  squares  are  made  both  unhardened 
and  hardened.  The  unhardened  form  has  graduations  on  one 
edge  and  is  termed  a  graduated  try  square.  The  hardened  type 


MACHINE  SHOP  WORK 


always  has  a  hardened  blade,  sometimes  a  hardened  beam  as  well, 
and  is  not  graduated. 

The  try  square  is  used  as  a  guide  to  draw  lines  at  right  angles 
to  each  other  and  to  given  surfaces;  to  erect  and  test  perpendic- 
ulars to  plane 
surfaces;  to  test 
the  truth  of  a 
given  surface  at 


N920 


THEL.S.STARRSTTCO. 


ATHOL  MASS.  U.S.A. 


right   angles    to 

another  surface;  in  short,  wherever  an  accurate  layout 
or  test  of  90  degrees  is  required.  When  used  for 
testing  the  relation  of  two  surfaces,  the  beam  is  pressed 
closely  against  the  correct  surface,  and  the  blade  is 
brought  carefully  down  to  the  surface  under  con- 
sideration. This  does  not  prove  more  than  that 
a  line  at  the  particular  point  tested  is  or  is  not  at 
right  angles  to  the  true  surface.  By  using  the  blade 
as  a  straightedge  parallel  to  the  true  surface,  errors 
in  that  direction  may  be  corrected  and  the  surface  be  made  plane. 
Bevel.  In  many  cases  it  is  necessary  to  test  the  relation  of 
lines  and  surfaces  which  are  not  at  right  angles  to  each  other.  For 


Fig.  7.     Steel 
Try  Square 


Fig.  8.     Universal  Bevel 
Courtesy  of  L.  S.  Stirrett  Company,  Athol,  Massachusetts 

this  purpose  a  bevel  is  used  in  which  what  corresponds  to  the  blade 
of  the  square  is  made  adjustable.  Its  construction  is  seen  in 
Fig.  8;  its  use  is  similar  to  that  of  the  square. 


6  MACHINE  SHOP  WORK 

Protractor.  The  bevel  can  be  adjusted  only  by  direct  appli- 
cation to  lines  or  surfaces  having  the  proper  angular  relation.  It 
often  happens  that  such  adjustment  is  not  feasible  and,  therefore, 
a  registering  device,  in  the  form  of  a  graduated  arc,  is  applied  to 
the  bevel,  making  what  is  known  as  a  protractor,  Fig.  9.  This 
tool  can  be  used  to  find  the  angular  relation  in  degrees  or  to  produce 
that  relation  by  setting  to  the  proper  point  on  the  graduated  arc. 

Center  Square.  As  the  center  of  a  circle  is  found  at  the  inter- 
section of  any  two  diameters,  an  instrument  for  readily  finding 
that  point  is  a  great  convenience.  In  Fig.  10  is  shown  a  combina- 
tion straightedge  and  square,  called  a  center  square,  which  accom- 
plishes this  result.  As  one  edge  of  the  rule  bisects  the  angle  of  the 
square,  it  is  evident  that  a  line  drawn  by  that  edge  passes  through 


Fig.  9.     Protractor 
Courtesy  of  L.  S.  Starrett  Company,  Athol,  Massachusetts 

the  center  of  any  circular  piece  to  which  the  square  is  applied. 
Locating  centers  in  the  ends  of  round  bars  or  circular  work  of  any 
kind  is  the  principal  use  of  this  tool. 

Combination  Set.  The  center  square,  bevel,  and  protractor 
are  furnished  in  a  combination  set  as  shown  in  Fig.  11.  The  ability 
to  change  the  length  of  the  blade  is  one  of  the  great  benefits  of  this 
construction. 

LINEAR  MEASUREMENT 

The  testing  tools  thus  far  described  are  used  for  comparing  the 
angular  relation  of  lines  and  surfaces  and  may  be  called  tools  for 
angular  measurement.  We  now  turn  to  the  consideration  of  instru- 
ments for  measuring  distances  and  sizes,  or  tools  for  linear  meas- 
urement. 


MACHINE  SHOP  WORK  7 

Carpenter's  Rule.  The  most  common  tool  for  linear  meas- 
urements, and  one  which  hardly  requires  description,  is  the  so-called 
carpenter's,  or  two-foot,  rule.  This  is  very  convenient  for  the 


Fig.  10.     Center  Square 


machinist  in  making  measurements  which  are  not  required  to  be 
very  accurate. 

Steel  Rule.    For  work  of  greater  refinement,  the  standard 
steel  rule,  Fig.  12,  is  used.    This  is  in  reality  a  graduated  straight- 


Fig.  11.    Combination  Set 
Courtesy  of  L.  S.  Starrelt  Company,  Athol,  Massachusetts 

edge  and,  as  such,  forms  a  part  of  several  tools  already  described. 
The  most  common  form  of  steel  rule  is  flat,  varying  from  1  to  48 
inches  in  length,  and  carefully  hardened  and  ground.  The  grad- 


s 


MACHINE  SHOP  WORK 


uations  in  the  better  class  of  rules  are  cut  with  a  dividing  engine, 
although  the  lines  may  be  etched  on  the  surface  with  a  fair  degree 
of  accuracy.  A  thin  and  somewhat  narrower  form,  called  a  flexible 
rule,  is  made  in  sizes  from  4  to  36  inches.  What  are  known  as  nar- 
row rules  are  obtainable  from  4  to  36  inches  and  are  of  great  con- 
venience in  certain  cases.  Besides  these  shapes,  square  rules  are 
made  in  sizes  from  3  to  6  inches  in  length,  and  the  triangular  form 
varies  in  length  from  3  to  12  inches.  Steel  rules  with  the  English 
system  of  graduation  can  be  obtained  with  the  inches  divided  in 
eighths,  sixteenths,  thirty-seconds,  sixty-fourths;  twelfths,  twenty- 
fourths;  tenths,  twentieths,  fiftieths,  and  hundredths.  Special 
rules  are  made  with  graduations  especially  adapted  to  such  uses  as 
gear  blank  sizing,  etc. 

The  ends  of  flat  rules  are  sometimes  graduated,  making  what 
might  be  called  a  very  short  rule  with  a  handle.     Flat  rules  are 


I   I   I   I  I 


111 


Fig.  12.     Steel  Rule 

sometimes  graduated  with  metric  divisions  as  fine  as  one  milli- 
meter, and  from  5  centimeters  to  1  meter  in  length. 

Dividers.  For  transferring  and  comparing  distances,  dividers 
are  commonly  used.  They  are  classified  according  to  the  style  of 
joint  and  the  length  of  the  leg.  The  most  simple  joint  is  the 
friction  and,  like  all  f rictional  devices,  is  hard  to  set  accurately.  Lock- 
joint  dividers  can  be  moved  freely  to  approximately  the  right 
position,  the  joint  locked,  and  the  adjusting  screw  used  for  the 
final  setting. 

Wing  dividers,  Fig.  13,  are  of  about  the  same  construction 
as  the  lock  joint,  except  that  the  fastening  is  made  on  the  wing 
instead  of  at  the  pivot.  The  best  of  all  forms  has  a  spring  adjust- 
ment as  shown  in  Fig.  14.  In  this  type,  a  spring  tends  to  open  the 
dividers,  and  the  legs  are  closed  against  the  spring  by  a  nut  working 
on  a  screw  which  is  fastened  to  one  leg  and  passes  freely  through 
the  other.  The  length  of  dividers  varies  from  2J  to  10  inches. 


MACHINE  SHOP  WORK 


9 


The  distance  to  which  dividers  can  be  opened  is  generally  about 
equal  to  the  length  of  the  leg.  For  distances  above  10  inches,  tram- 
mel points,  Fig.  15,  are  convenient.  They  consist  of  hardened 
steel  points  attached  to  metal  sockets  and  can  be  used  on  rods  of 
any  length.  One  point  may  have  a  spring  adjustment  and,  in 
that  case,  can  be  set  in  the  same  manner  as  a  pair  of  wing  dividers. 


Fig.  13.     Wing  Dividers 


Fig.  14.     Tool-Makers'  Dividers 
Courtesy  of  Brown  and  Sharpe  Manu- 
>        -  facturing  Company,  Provi- 
dence, Rhode  Island 


Calipers.  Outside  and  Inside  Calipers.  Instead  of  having 
straight  legs  with  sharp  points,  caliper  legs  are  bent  and  have  blunt 
points.  As  distances  are  to  be  measured  both  outside  and  inside 
of  solid  bodies,  we  have  outside  and  inside  calipers.  The  legs  of 
outside  calipers  have  a  large  curvature  so  that  the  calipers  may  be 
passed  over  cylinders  of  their  greatest  capacity. 

Inside  calipers,  Fig.  16,  are  much  like  dividers  in  general  appear- 
ance, the  ends  being  bent  outward  slightly  and  the  points  rounded. 
The  same  styles  of  joints  used  in  dividers  are  used  in  calipers,  and 


10 


MACHINE  SHOP  WORK 


Fig.  15.     Steel  Beam  Trammels 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  Island 


Fig.  16.     Brown  and  Sharpe  Inside 
Transfer  Calipers 


Fig.  17.     Brown  and  Sharpe'Outside 
Transfer  Calipers 


MACHINE  SHOP  WORK 


11 


the  size  of  calipers  is  also  designated  by  the  distance  from  the  joint 
to  the  end  of  the  leg.  Spring  calipers  are  made  in  sizes  from  2J 
to  8  inches,  while  the  other  styles  vary  up  to  24  inches. 

Transfer  Calipers.  As  it  is  sometimes  necessary  to  make 
measurements  behind  shoulders  and  in  chambered  cavities  where 
the  ordinary  calipers  could  not  be  removed  after  setting,  it  is  neces- 
sary to  have  calipers  so  arranged  that  they  may  be  set,  changed  to 
clear  the  obstruction,  and  then  reset  accurately  in  the  first  position. 
This  is  accomplished  by  transfer  calipers,  Fig.  17,  in  which  one 
leg  is  temporarily  fastened  to  a  stub  or  false  leg.  After  setting, 
this  leg  may  be  moved  away  from  the  stub,  the  calipers  withdrawn, 
and  the  leg  again  placed  in  contact  with  the  stub;  the  points  will 
then  be  found  to  occupy  the 
same  position  as  when  first 
set.  Small  curved  legs  may 
be  used  in  place  of  points  or 
trammels  in  calipering  large 
objects. 

Both  dividers  and  cali- 
pers are  usually  set  by  means 
of  a  scale.  In  setting  divi- 
ders, place  one  point  in  a 
graduation  of  the  scale  and 
move  the  other  until  it  falls 
easily  into  another  graduation  which  gives  the  required  distance. 
Outside  calipers  are  often  set  by  placing  one  leg  against  the  end 
of  the  scale  and  moving  the  other  until  it  is  opposite  the  middle 
of  the  graduation  giving  the  required  length.  As  the  graduations 
are  not  mathematical  lines  but  have  an  appreciable  width,  this 
last  precaution  is  one  of  great  importance.  Inside  calipers  are 
set  by  placing  both  the  scale  and  the  caliper  toe  against  a  plane 
surface,  as  shown  in  Fig.  18;  the  other  toe  is  then  set  the  same  as 
the  outside  caliper. 

Caliper  legs  are  comparatively  slender,  spring  easily,  and  care 
must  be  taken  in  using  them  to  see  that  the  contact  with  the  object 
being  tested  is  very  light.  It  is  an  easy  matter  to  spring  calipers 
of  common  sizes  as  much  as  one-sixteenth  of  an  inch  unless  a 
gentle  touch  is  used  in  handling  them, 


Fig.   18.     Setting   Inside  Calipers 


12 


MACHINE  SHOP  WORK 


Caliper  Square.  The  caliper  square  is  made  by  attaching  a 
movable  blade  to  the  common  square.  In  the  ordinary  forms  it 
closely  resembles  a  steel  rule  with  ^two  arms  extending  from  it  at 
right  angles,  one  fixed  near  the  end  and  the  adjustable  arm  sliding 
along  the  scale  with  a  clamping  device  for  adjusting  this  movable 
arm.  In  order  that  the  movable  arm  may  be  set  accurately,  caliper 
squares,  Fig.  19,  as  at  present  constructed  have  two  clamps  for  the 
movable  arm.  The  one  carrying  the  thumb  nut  is  to  be  first  clamped 
in  approximately  the  right  position,  the  clamp  on  the  movable 
arm  being  secured  after  the  adjustment  has  been  made  by  the  nut. 


Fig  19.     Caliper  Square 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  Island 

The  sizes  used  vary  from  3  inches  up,  and  are  limited  only  by  the 
length  of  rule  obtainable. 

Micrometers.  For  measurements  which  are  required  to  be 
more  accurate  than  can  be  obtained  by  the  preceding  forms  of 
calipering  devices,  the  micrometer  caliper,  Fig.  20,  is  used.  The 
accuracy  of  its  measurements  is  determined,  not  by  direct  setting 
to  two  lines,  but  by  finely  dividing  the  pitch  of  the  measuring  screw 
and  furnishing  means  for  reading  these  subdivisions.  It  is  a  regis- 
tering as  well  as  an  indicating  caliper,  and  thus  serves  the  purpose 
of  a  common  caliper  in  combination  with  a  rule,  but  with  a  much 
greater  degree  of  accuracy. 

The  micrometer  caliper  consists,  essentially,  of  a  crescent- 
shaped  frame  carrying  a  hardened  steel  anvil  B  at  one  end  and  a 


MACHINE  SHOP  WORK  13 

nut  of  fine  pitch  at  the  other,  the  axis  of  the  nut  being  at  right  angles 
to  the  face  of  the  anvil.  The  outside  of  the  nut  A  forms  a  pro- 
jection beyond  the  crescent  that  is  called  the  barrel.  The  measuring 
screw  consists  of  a  fine-pitched  screw  to  fit  the  nut,  combined  with 
a  measuring  point  (7,  having  a  face  parallel  with  that  of  the  anvil. 
Firmly  attached  to  the  outer  end  of  this  screw  is  a  thimble  D,  fitting 
closely  over  the  barrel;  the  edge  of  this  thimble  is  beveled  so  that 
graduations  placed  on  the  edge  come  very  close  to  the  barrel.  A 
reference  line  is  drawn  on  the  barrel  parallel  to  its  axis  and  graduated 
to  represent  the  pitch  of  the  screw.  The  chamfered  edge  of  the 
thimble  is  so  divided  that  the  movement  of  one  division  past  the 
reference  line  on  the  barrel  indicates  a  movement  of  the  measuring 


Fig.  20.     Transparent  View  of  Micrometer  Caliper  with  Friction  Stop 
Courtesy  of  L.  S.  Starrett  Company,  Athol,  Massachusetts 

point  of  one-thousandth  of  an  inch.  For  example:  if  the  pitch 
of  the  measuring  screw  is  one-hundredth  of  an  inch,  there  should 
be  10  divisions  on  the  thimble,  if  one-fiftieth  of  an  inch,  20  divisions; 
if  one-fortieth  of  an  inch,  25  divisions;  if  one  twenty-fifth  of  an 
inch,  40  divisions.  Measuring  screws  having  a  pitch  of  one-fortieth 
of  an  inch  are  usually  used,  and  every  fourth  division  on  the 
barrel  lengthened  and  numbered  to  indicate  tenths  of  an  inch,  as 
shown  in  Fig.  21. 

In  using  the  micrometer  caliper,  it  should  not  be  set  at  the 
size  required  and  pushed  over  the  work,  but  should  first  be  opened, 
then  screwed  down  until  the  measuring  point  C  and  anvil  B  are 
in  contact  with  the  work;  the  size  may  then  be  read  from  the  relation 
of  the  thimble  to  the  reference  line  on  the  barrel.  The  proper  degree 


14 


MACHINE  SHOP  WORK 


of  pressure  to  be  applied  to  the  screw  is  acquired  only  after  extended 
practice,  and  some  manufacturers  place  a  friction  device  on  the 
thimble  so  that  undue  pressure  cannot  be  exerted. 

The  micrometer  caliper  will  not  only  indicate  that  the  work 
is  too  large  or  too  small,  but  will  also  show  exactly  the  amount 
by  which  it  differs  from  the  desired  measurement.  This  is  a  great 
improvement  over  the  rigid  form  of  calipers,  and  enables  the  work- 
man to  judge  more  accurately  the  progress  of  the  work.  As  the 
micrometer  caliper  is  rapidly  coming  into  favor  in  spite  of  its  cost, 
it  has  been  described  more  at  length  than  the  'common  forms  pre- 
viously considered. 

The  range  of  motion  of  the  measuring  screw  is  usually  limited 
to  one  inch,  but  various  devices  give  the  micrometer  caliper  a 


Fig.  21.     Ordinary  Micrometer  Caliper  Showing  Typical  Reading 

larger  range  of  action.    Micrometer  calipers  may  now  be  purchased 
in  combinations  or  sets,  with  a  range  from  zero  to  20  inches. 

The  application  of  the  micrometer  principle  to  inside  meas- 
urements is  not  in  general  use,  but  is  easy  to  arrange,  and  makes 
a  very  simple  instrument)  as  shown  in  Fig.  22.  It  consists  of  an 
ordinary  micrometer  head,  except  that  the  outer  end  of  the  thim- 
ble carries  a  contact  point,  attached  to  a  measuring  rod  which 
may  be  of  any  length.  The  shortest  distance  that  can  be  measured 
with  this  device  is  about  2  inches,  but  there  is  hardly  any  limit  in 
length,  as  the  rigidity  of  the  rod  is  easily  provided  for.  It  is  evi- 
dent that  such  rigidity  is  harder  to  obtain  in  the  curved  shape 
necessary  for  outside  measurement  and  thus  limits  this  form  to 
about  20  inches,  as  above  stated.  The  contact  points  in  the 
outside  type  are  parallel  plane  surfaces,  and  in  the  inside  form  they 


MACHINE  SHOP  WORK 


15 


are  rounded  points  of  small  radius.  Outside  micrometers  are  pro- 
vided with  contact  points  of  varying  forms  for  measuring  paper, 
threads,  walls  of  tubes,  etc. 

Reading  the  Micrometer.  Reading  in  thousandths.  As  stated, 
the  micrometer  screw  has  usually  forty  threads  per  inch  and  the 
thimble  has  twenty-five  divisions  on  its  circumference.  The  barrel 
is  divided  to  correspond  to  the  pitch  of  the  screw  with  each  fourth 
division  numbered.  In  reading  the  indicated  measurement,  first 
note  the  highest  number  visible  on  the  barrel  and  call  it  hundreds 


Fig.  22.     Inside  Micrometers 
Courtesy  of  L.  S.  Starrett  Company,  Athol,  Massachusetts 

of  thousands — in  Fig.  21  it  is  400  thousandths  or  .400;  then 
read  the  short  divisions  on  the  barrel,  calling  the  first  division  25 
thousandths,  or  .025;  the  second,  50  thousandths,  or  .050;  and  the 
third,  75  thousandths,  or  .075.  In  Fig.  21  the  third  division  is  the 
last  one  visible.  Now  read  the  number  indicated  on  the  thimble, 
that  is,  the  number  that  has  passed  the  line  running  lengthwise.  In 
the  figure  it  is  16;  or  16i  if  the  reading  is  to  be  finer  than  thousandths. 
Add  this  reading  to  the  readings  of  the  short  divisions,  thus:  75+ 
16i  =  91i;  this  is  .09H.  Adding  the  .400  to  this  we  get  .491 J.  This 
means  that  the  distance  from  the  anvil  to  the  measuring  point  is 


16 


MACHINE  SHOP  WORK 


T4oVoir  of  an  inch,  or  .4915  inch.  If  the  micrometer  caliper  is  a 
good  one,  we  may  be  sure  the  distance  is  between  .491  inch  and 
.492  inch. 

Reading  to  Ten-Thousandths.  In  reading  measurements  finer 
than  thousandths,  use  is  made  of  a  Vernier.  The  following  descrip- 
tion tells  how  to  read  a  ten-thousandths  micrometer:  As  applied  to 
a  micrometer,  the  Vernier  consists  of  ten  divisions  on  the  sleeve 
which  occupy  the  same  space  as  nine  divisions  on  the  thimble.  The 
difference  of  width  of  one  of  the  ten  spaces  on  the  sleeve  and  one  of 
the  nine  spaces  on  the  thimble  is  one-tenth  of  a  space  on  the  thimble. 
In  Fig.  23  at  B,  the  third  line  from  the  zero  on  the  thimble  coincides 
with  the  first  line  on  the  sleeve.  In  opening  the  tool  by  turning  the 


THIMBLE  THIMBLE 

O  in  /-I  Q 


°       10       o  2       to       o 


B 


Fig.  23.     Diagrams  Showing  How  to  Read  Micrometer  Caliper 

thimble  to  the  left,  each  space  on  the  thimble  represents  an  opening 
of  the  tool  equal  to  one-thousandth  of  an  inch.  If  the  thimble  be 
turned  so  the  lines  marked  5  and  2  coincide,  the  tool  will  have  been 
opened  two-tenths  of  one-thousandth,  or  2  ten-thousandths.  At  C 
the  thimble  has  been  turned  until  line  10  matches  with  line  7  on  the 
sleeve.  The  tool  has  therefore  been  opened  7  ten-thousandths. 
Therefore,  first  note  the  thousandths  as  in  reading  the  ordinary 
micrometer,  then  observe  the  line  on  the  sleeve  which  matches  with  a 
line  on  the  thimble.  If  it  is  the  second  line,  marked  1,  add  one 
ten-thousandth  to  the  previous  reading;  if  the  third  line,  marked  2, 
add  2  ten-thousandths,  etc. 

Vernier  Calipers.  A  common  use  of  a  Vernier  is  its  application 
to  a  caliper  square,  termed  a  Vernier  caliper.  Fig.  24  shows  a  repre- 
sentative tool. 


MACHINE  SHOP  WORK 


17 


How  to  Read  the  Vernier.  The  following  text  represents  the 
L.  S.  Starrett  instructions  for  reading  their  tool: 

The  scale  of  the  tool  is  graduated  in  fortieths,  or  .025  of  an  inch,  every 
fourth  division,  representing  a  tenth  of  an  inch,  being  numbered.  On  the  Ver- 
nier plate  is  a  space  divided  into  twenty-five  parts  and  numbered  0,  5,  10,  15, 
20,  25.  The  twenty-five  divisions  on  the  Vernier  occupy  the  same  space  as  the 
twenty-four  divisions  on  the  scale. 

The  difference  between  the  width  of  one  of  the  twenty-five  spaces  on  the 
Vernier  and  one  of  the  twenty-four  spaces  on  the  scale  is,  therefore,  ^s  of  4*0,  or 


Fig.  24.     Front  and  Back  View  of  Vernier  Caliper 
Courtesy  of  L.  S.  Starrett  Company,  Athol,  Massachusetts 


of  an  inch.  If  the  Vernier  is  set  so  that  the  0  line  on  the  Vernier  coincides 
with  the  0  line  on  the  scale,  the  next  two  lines  will  not  coincide  by  TOGO  of  an 
inch;  the  next  lines  will  be  two  thousandths  apart,  and  <  o  on. 

To  read  the  tool,  note  how  many  inches — tenths,  or  .100,  and  fortieths,  or 
.025 — the  0  mark  on  the  Vernier  is  from  the  0  mark  on  the  scale;  then  note  the 
number  of  divisions  on  the  Vernier  from  0  to  a  line  which  exactly  coincides  with 
a  line  on  the  scale. 

In  Fig.  25  the  Vernier  has  been  moved  to  the  right  one  and  four-tenths  and 
one-fortieth  inches  (1.425"),  as  shown  on  the  scale,  and  the  eleventh  line  on  the 
Vernier  coincides  with  a  line  on  the  scale.  Eleven  thousandths  of  an  inch  are 
therefore  to  be  added  to  the  reading  on  the  scale,  and  the  total  reading  is  one  and 
four  hundred  and  thirty-six  thousandths  inches  (1.436"),  which  is  the  distance 
the  jaws  of  the  tool  have  been  opened. 


18 


MACHINE  SHOP  WORK 


In  making  inside  measurements,  the  width  of  the  jaws,  as  given  in  the  list, 
to  be  added  to  the  apparent  readings  on  the  side  having  the  Vernier  to  allow 

for  the  space  occupied  by  the  meas- 
uring points.  No  such  allowance  is 
necessary  when  using  the  back  side, 
without  Vernier,  as  the  two  lines 
marked  "in"  and  "out"  indicate  inside 
and  outside  measurements. 

EXAMPLES  FOR  PRACTICE 

1.  A  micrometer  caliper  shows  a 
reading  of  .463;  how  many  times  must 
the  thimble  be  turned  to  produce  a 
reading  of  .587?  (Assume  40  threads 
per  inch.)  Ans.  4|^  times 

2.  What  are  the  readings  of  the  micrometer  calipers  shown  in  Figs.  26 
and  27?  Ans.  .039 

3.  State  the  readings  of  the  micrometer  calipers  shown  in  Figs.  28  and  29. 

Ans.  .1546 


Fig.  25.     Enlarged  View  of  Vernier 


,u 


Figs.  26  and  27.      Positions  of  Caliper  for          Figs.  28  and  29.     Positions  of  Caliper  for 
Example  2  Example  3 


4.  Give   the    readings   of   the   micrometer    calipers    shown  in  Figs.  30 
and  31.  Ans.  .7398 

5.  Ske    h  the  front  and  back  of  a  micrometer  caliper  when  the  reading 
is  .6327. 

6.  Wha ,  is  the  reading  of  the  Vernier  and  scale  when  in  position  Fig.  32? 

Ans.  6.36 

Fixed  Gages.  While  the  adjustable  tools  just  described  are 
available  for  a  large  range  of  work,  gages  of  one  dimension,  or  fixed 
gages,  are  used  to  a  considerable  extent,  especially  in  shops  where 
work  of  a  duplicate  character  is  produced  in  large  quantities.  These 
may  be  used  for  standards  to  which  adjustable  gages  may  be  set, 


MACHINE  SHOP  WORK 


19 


1/7, 


or  used  directly  in  connection  with  the  work  in  the  same  manner  as 
an  adjustable  gage.  One  form  of  such  gages  for  comparisons  of 
length  is  a  steel  rod  with  the  ends 
carefully  ground  so  that  the  distance 
required  may  be  quickly  and  accu- 
rately determined.  In  one  form  the 
ends  are  parallel  plane  surfaces, 
and  in  another  the  ends  are  sec- 
tions of  a  sphere  of  the  same  diam- 
eter as  the  length  of  the  rod.  Both 
these  forms  are  illustrated  in  Fig.  33. 
Another  form  of  gage  for  the  same 
purpose  consists  of  hardened  and 
ground  steel  discs,  Fig.  34,  to  which 
calipers  and  similar  tools  may  be 
set,  and  which  may  be  used  also  to 
test  the  size  of  holes  by  direct  application.  For  the  latter  purpose, 
handles  are  provided  by  which  the  discs  can  be  conveniently 
manipulated. 

Plug  and  Ring  Gages. 
Plug  and  ring  gages,  Fig. 
35,  furnish  accurate  and 
convenient  standards  for 

Fig.  32.     Position  of  v  ermer  for  Example  6 

the  production  of  dupli- 
cate parts  of  machines.    The  same  result  is  attained  by  the  caliper 
gage,  Fig.  36,  which  combines  the  two  gages  in  one  piece.     In 


u 


Figs.  30  and  31.     Positions  of  Caliper 
for  Example  4 


^r^J 

G 

0 

1   2  3 

A  5  6  7  8  9  10 

*-*. 

| 

1    1    1 

|    | 

1    1     1 

Mill 

!  1 

1     1 

^ 

1     1     1 

1 

1     1 

1    1 

1 

•    Z    3   4 

5   6 

769 

•    3345 

e  7 

6    9 

^ 

Fig.  33.     End  Measuring  Rods 

this  form  the  external  gage  has  parallel  plane  surfaces  and  the 
internal  gage  is  a  section  of  a  cylinder.     In  sizes  above  3  inches, 


20 


MACHINE  SHOP  WORK 


the  caliper  gage  is  usually  made  in  two  parts,  making  the  tool  easier 

to  handle. 

As  is  indicated  by  the  cost  of  these  gages,  the  exact  duplication 

of  such  exact  sizes  in  quantities  would  mean  a  cost  that  would  be 

prohibitive  in  machine  con- 
struction. The  limit  of  error 
in  the  standard  gages  just 
described  is  never  over  one 
ten-thousandth  of  an  inch  at  a 
standard  temperature,  which  is 
usually  taken  as  70°  F.  Ordi- 
nary machine  parts  do  not 
require  such  accuracy,  and  it  is 
usual  to  allow  a  limit  of  error 
which  is  in  accordance  with  the 
class  of  work  being  produced. 
Limit  Gages.  For  testing  sizes  and  dimensions,  both  at  the 

machine  and  in  the  inspection  department,  combination  fixed  gages, 


Fig.  34.     Set  of  Ground  Steel  Disc  Gages 

Courtesy  of  Brown  and  Sharpe  Manufacturing 

Company,  Providence,  Rhode  Island 


Fig.  35.     Typical  Plug  and  Ring  Gages 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  Island 


Fig.  36.     Caliper  Gages 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  Island 

known  as  limit  gages,  are  employed.    These  are  made  both  for 
external  and  internal  measurements.     The  external  gage,  Fig.  37,  is 


MACHINE  SHOP  WORK 


21 


for  testing  pieces  supposed  to  be  .250  inch  in  diameter.  As  indicated 
by  the  figures  on  the  gage,  the  piece  is  allowed  a  variation  of  .0005 
inch  over  and  .001  inch  under  the  nominal  size.  The  words  "go  on" 
and  "not  go  on",  stamped  near  the  ends,  indicate  clearly  how  the 


Fig.  37.     Limit  Gage  with  Jaws  Opposite 


Fig.  38.     Limit  Gage  with  Jaws  in  Series 


Fig.  39,     Limit  Gage  for  Holes 


gage  is  used.  A  more  convenient  arrangement  of  this  gage  is  shown 
in  Fig.  38,  in  which  the  work  must  enter  the  first  parallel  opening, 
but  must  not  pass  through  the  second.  In  this  form,  one  motion 
tests  the  piece  for  variation  above  and  below  the  standard.  Fig.  39 
shows  a  limit  gage  for  holes, 
the  end  marked  "go  in" 
being  required  to  pass  into 
the  hole,  while  the  other 
end,  marked  "not  go  in", 
must  not  enter.  An  arrange- 
ment of  the  internal  limit  gage  similar  to  the  external  gage  of  Fig.  38 
is  shown  in  Fig.  40,  and  has  the  same  advantages. 

In  some  classes  of  work  no  variation  is  allowed  over  the  stand- 
ard size,  and  in  other  classes  no  variation  is  allowed  under  the  nom- 
inal size.  The  amount  of 
variation  allowed  in  any 
case  is  governed  by  the  class 
of  work  and  the  intended 
use  of  the  piece.  As  these 
allowances  are  not  uniform, 
such  gages  are  not  kept  in  stock  but  are  made  only  'to  order. 

For  many  years  gages  of  an  entirely  different  character  have 
been  used  in  the  measurement  of  wire,  small  rods,  and  sheet  metal. 
The  sizes  have  been  designated,  not  by  the  diameter  or  any  definite 
unit,  but  by  a  number  or  letter  in  a  purely  arbitrary  manner.  Even 
in  the  same  gage,  the  sizes  do  not  advance  in  any  regular  order. 


Fig.  40.     Limit  Gage  for  Holes  with  Limits 
in  Series 


22 


MACHINE  SHOP  WORK 


The  matter  is  still  further  complicated  by  the  fact  that  in  one  gage 
large  numbers  indicate  large  sizes,  while  in  another,  the  smaller 
numbers  mark  the  large  diameters.  Another  source  of  annoyance 

lies  in  the  fact  that  such 
gages  are  cheaply  made 
and  cannot  be  relied 
upon  to  be  duplicates  of 
one  another.  Most  of 
these  gages  had  their 
origin  in  days  when 
refined  measurements 

Fig.  41.     Cast-Iron  Surface  Plate  Were    Hot     Common,    but 

Courtesy  of  Brown  and  Sharpe  Manufacturing  Company.  .  ,  „        , 

Providence,  Rhode  Island  Since      the      US6     Oi      the 

micrometer    caliper   has 

become  almost  universal,  there  seems  to  be  no  good  reason  why  all 
sizes  should  not  be  expressed  in  thousandths  of  an  inch,  thus  avoiding 

the  troubles  incident  to 
the  use  of  the  arbitrary 
gages. 

Surface  Plates.    For 
the  production  of  accurate 
plane  surfaces  the  use  of 
the   straightedge    is    not 
sufficient.    Such  surfaces 
should  be  compared  with 
standard  surfaces,  called 
surface  plates,  Fig.  41.   A 
surface  plate   is   a   cast- 
iron  plate  strongly  ribbed 
on  the  back  to   prevent 
distortion,  and  supported 
on  three  points  to  insure  a 
uniform  base.     Their  pro- 
duction and  use  will  be 
described  under  the  head  of   "Scraping".     They  may  be  had  in 
sizes  varying  from  3  inches  by  4  inches  to  36  inches  by  72  inches. 
Work  Bench.    The  machinist's  bench  at  which  hand  work  is 
ordinarily  performed  shoulcl  be  of  substantial  character,  about  2 


Fig.  42.     Work  Bench 

Courtesy  of  Brown  and  Sharpe  Manufacturing  Com- 
pany, Providence,  Rhode  Island 


MACHINE  SHOP  WORK 


23 


feet  10  inches  from  the  floor  and  2  feet  3  inches  wide,  Fig.  42.  For 
the  sake  of  economy  it  is  usual  to  have  a  2J-  or  3-inch  plank  at  the 
front  to  which  the  vises  are  fastened  and  on  which  all  the  heavy  work 
is  done,  while  the  rear  of  the  bench  is  made  from  1-inch  lumber.  Maple 
and  birch  are  preferred  as  materials  for  a  bench,  although  ash  makes 
a  very  good  substitute. 

Work  Vises.  In  order  that  work  may  be  held  rigidly  for  the 
performance  of  hand  operations,  the  machinist  uses  what  is  termed 
a  vise.  They  are  made  in  a  great  variety  of  forms  and  sizes,  but  all 


Fig.  43.     Bench  Vise 

consists  essentially  of  a  fixed  jaw,  a  movable  jaw,  a  screw,  a  nut  fas- 
tened to  the  fixed  jaw,  and  a  handle  by  which  the  screw  is  turned 
in  the  nut  and  the  movable  jaw  brought  into  position.  The  sec- 
tional view,  Fig.  43,  shows  these  parts  clearly  and  also  a  device, 
present  in  some  form  in  all  vises,  by  which  the  movable  jaw  is  sep- 
arated from  the  fixed  jaw  when  the  screw  is  backed  out  of  the  nut. 
In  the  machinist's  vise,  both  jaws  are  made  of  cast  iron  with 
removable  faces  of  cast  steel.  These  may  be  .checkered  to  provide 
a  firm  grip  for  heavy  work,  or  may  be  smooth  to  avoid  marking  the 
surface  of  the  plate  operated  upon.  When  holding  soft  metal,  even 


24 


MACHINE  SHOP  WORK 


the  smooth  steel  jaws  would  mar  the  surface;  and  in  such  cases  it  is 
customary  to  use  false  jaws  of  brass  or  Babbitt  metal,  or  to  fasten 
leather  or  paper  directly  to  the  steel  jaws.  The  screw  and  handle 
are  made  from  steel  and  the  nut  from  malleable  iron. 

The  common  method  of  fastening  a  vise  to  the  bench  is  by 
means  of  the  fixed  base  shown  in  Fig.  43,  although  a  swivel  base 
such  as  is  shown  in  Fig.  44  is  preferable.  The  vise  shown  in  Fig.  44 
also  has  a  swivel  jaw,  which  enables  it  to  hold  tapered  work  securely. 
This  swivel  jaw  is  provided  with  a  locking-pin,  which  fixes  the  jaws 


Fig.  44.     Swivel  Work  Vise 

in  a  parallel  position.  The  height  of  the  vise  from  the  floor  depends 
somewhat  on  the  class  of  work  to  be  performed,  but  a  general  rule 
is  to  have  the  top  of  the  jaws  about  1J  inches  below  the  point  of  the 
elbow  when  standing  erect  beside  the  vise. 

HAMMERS 

Classification.  The  machinist  uses  hammers  of  three  shapes: 
ball  peen,  cross  peen,  .and  straight  peen,  Fig.  45.  The  ball  peen  is 
the  most  common;  it.  varies  in  weight  from  4  ounces  to  3  pounds. 
The  cross  peen  and  straight  peen  hammers  vary  from  4  ounces  to  2 
pourujs  and  are  used  principally  in  riveting.  Hammers  are  made 


MACHINE  SHOP  WORK  25 

from  a  good  grade  of  tool  steel,  hardened,  and  drawn  to  a  blue 
color  at  the  eye  and  a  dark  straw  on  the  face  and  peen.  The  eye  is 
elliptical  in  shape,  and  the  handle  is  fastened  by  driving  wedges, 
either  wood  or  iron,  into  the  end  of  the  handle,  thus  spreading  it  to 
fill  the  eye.  The  handle  is  of  hard  wood,  preferably  hickory,  and  of 
a  length  suited  to  the  weight  of  the  hammerhead.  When  the  handle 
is  properly  inserted,  the  axis  of  the  head  stands  at  right  angles  to 
the  axis  of  the  handle. 

Soft  Hammers.  Soft  hammers  are  used  for  striking  heavy 
blows  where  the  steel  hammer  would  bruise  the  metal  or  mar  the 
surface.  They  are  made  of  rawhide,  copper,  or  Babbitt  metal,  and 
vary  in  weight  from  6  ounces  to  6  pounds.  They  are  subject  to 


Fig.  45.     Hand  Hammers 

rapid  wear,  but  are  indispensable  in  setting  up  and  taking  down 
machinery.  Those  of  metal  are  so  constructed  that  the  soft  metal 
can  be  recast  in  the  handle/ 

CUTTING  TOOLS 

Chisels.  The  simplest  form  of  metal-cutting  tool  is  the  chisel. 
The  several  types  in  common  use  are  shown  in  Fig.  46. 

Flat  Chisel.  The  flat  chisel  is  used  for  snagging  castings,  for 
chipping  surfaces  having  less  width  than  the  edge  of  the  chisel,  and 
for  all  general  chipping  operations.  It  is  the  form  most  commonly 
used,  and  is  often  called  the  cold  chisel.  Generally  it  has  a  cutting 
edge  about  an  eighth  of  an  inch  wider  than  the  stock  from  which  it 
is  forged. 

Cape  Chisel.  The  cape  chisel  is  used  for  cutting  keyways, 
channels,  etc.,  and  also  for  breaking  up  surfaces  too  wide  to  chip 
with  the  flat  chisel  alone.  Channels  are  driven  across  such  a  sur- 
face, leaving  raised  portions  or  "lands"  to  be  removed  by  the  flat 


26 


MACHINE  SHOP  WORK 


chisel.  The  cutting  edge  of  this  chisel  is  usually  an  eighth  of  an 
inch  narrower  than  the  shank,  and  the  part  just  in  the  rear  of  the 
cutting  edge  is  made  thin  enough  to  avoid  binding  in  the  slot.  As 
this  weakens  the  chisel,  it  is  made  comparatively  thick  in  the  plane 
at  right  angles  to  the  cutting  edge. 

Diamond  Point.  The  diamond  point  chisel  is  made  by  drawing 
out  the  end  of  the  stock  to  about  -fg  inch  square,  and  grinding  the 
end  at  an  angle  with  the  axis  of  the  chisel,  leaving  a  diamond-shaped 
point.  It  is  used  for  drawing  holes,  making  oil  grooves,  and  cutting 
holes  in  flat  plates. 

Round  Nose.  The  small  round-nosed  chisel  is  cylindrical  in 
section  near  the  cutting  end,  the  edge  being  ground  at  an  angle  of 
60  degrees  with  the  axis  of  the  chisel.  When  used  to  "draw"  the 
starting  of  drilled  holes  to  bring  them  concentric  with  the  drilling 


Fig.  46.     Hand  Chisels 

circles,  they  are  called  center  chisels.  The  round-nosed  chisel  is 
also  used  for  cutting  channels,  such  as  oil  grooves  and  similar  work. 
The  larger  sizes  of  round-nosed  chisels  are  of  the  general  shape  of 
the  cape  chisel  with  one  edge  rounded,  making  a  convex  cutting 
edge.  Large  round  bottomed  channels  and  all  concave  surfaces  are 
the  proper  work  of  the  round-nosed  chisel. 

All  the  accompanying  forms  should  be  made  from  a  good  grade 
of  tool  steel,  carefully  forged,  hardened,  and  tempered  to  a  purple 
color.  The  stock  generally  used  is  octagonal,  and  the  chisels  for 
heavy  work  are  about  8  inches  long  and  f  inch  in  diameter. 

Cutting  Edge  of  Chisel.  The  two  bevels  forming  the  cutting 
edge  of  a  chisel  should  make  with  each  other  as  small  an  angle  as  is 
possible  without  leaving  the  cutting  edge  weak.  If  the  angle  is  too 
small,  the  chisel  will  soon  become  dull,  while  if  large,  more  force  will 


MACHINE  SHOP  WORK 


27 


be  required  to  drive  it.     The  best  angle  for  cutting  cast  iron,  all 

things  considered,  is  about  70  degrees,  while  for  wrought  iron  and 

mild  steel  a  slightly  smaller  angle,  say  60  degrees,  will  be  better. 

When  there  are  two  bevels,  they  should  be  alike  in  width  and  form 

equal  angles  with  the  center  line  of  the  chisel.    Small  round-nosed 

chisels  and  some  slotting  chisels  are  ground  one-sided,  that  is,  with 

but  one  bevel  like  a  wood  chisel.    The  angle  between  the  surfaces 

which  form  the  cutting 

edge  should  be  the  same, 

whether  these    surfaces 

are  both  bevels,  or  one 

a  bevel  and  the   other 

"the  straight  side  of  the 

chisel.      In  a  one-sided 

chisel,  therefore,  the 

angle     that     the    bevel 

forms  with  the  center  line 

of  the  chisel  should  be 

twice  as  large  as  in  one 

having  two  bevels. 

To  cut  well,  chisels 
should  be  sharp  and, 
therefore,  should  be 
ground  at  once  when 
they  become  dull.  This 
may  be  done  on  an 
emery  or  carborundum 
wheel,  not  finer  than 
No.  60,  care  being  taken 
to  avoid  heating,  which  draws  the  temper  and  spoils  the  tool. 

Chipping.  Chipping  is  a  term  applied  to  the  removal  of  metal 
with  the  cold  chisel  and  hammer.  The  degree  of  accuracy  required 
varies.  The  piece  is  held  in  a  vise,  and  the  method  of  working  is  to 
grasp  the  chisel  firmly  with  the  left  hand,  holding  the  cutting  edge 
to  the  work  and  striking  the  head  of  the  chisel  with  the  hammer, 
keeping  the  eyes  on  the  edge  of  the  chisel  to  watch  the  progress  of 
the  work,  Fig.  47.  The  lower  side,  or  bevel  of  the  chisel,  is  the  guid- 
ing surface  and  is  held  at  a  very  slight  angle  with  the  finished  portion 


Fig.  47.     Bench  Chipping 


28  MACHINE  SHOP  WORK 

of  the  work,  the  cutting  edge  only  touching.  Raising  or  lowering 
the  shank  of  the  chisel  increases  or  decreases  the  inclination  of  the 
guiding  bevel  and  causes  the  chisel  to  take  a  heavier  or  lighter  cut. 
If  the  hand  is  carried  too  low,  the  chisel  will  run  out  before  the  end 
of  the  cut;  while  if  the  hand  is  raised  too  high,  the  progress  will  be 
slow,  owing  to  the  resistance  offered  by  the  metal  to  separation. 
The  depth  of  the  cut  taken  with  a  cold  chisel  should  never  be  more 
than  an  eighth  of  an  inch. 

When  chipping  wrought  iron  or  steel,  a  piece  of  waste  saturated 
with  oil  should  be  kept  on  the  bench  and  the  edge  of  the  chisel  fre- 
quently thrust  into  it.  This  lubricates  the  surfaces  in  contact  and 
preserves  the  cutting  edge  of  the  chisel.  While  lines  are  used  as 
guides  in  chipping  operations,  it  is  never  advisable  to  bring  the 
surfaces  too  near  them  with  the  chisel;  sufficient  stock  must  be  left 
so  that  the  surfaces  may  be  finished  with  a  file.  This  is  especially 
to  be  observed  in  chipping  keyways  with  a  cape  chisel;  an  ample 
margin  for  filing  should  be  left  both  on  the  sides  and  on  the  bottom. 

F.LES 

Characteristics.  The  file  differs  from  the  chisel  in  having  a 
large  number  of  cutting  points  instead  of  one  cutting  edge  and  in 


Fig.  4,8.     Hand  File 

being  driven  directly  by  the  hand  instead  of  by  the  hammer.  As 
hand  power  only  is  used,  it  is  evident  that  the  amount  of  metal 
removed  at  one  stroke  will  be  small,  and  the  amount  removed  by  a 
single  tooth  will  be  exceedingly  small. 

Files  are  made  from  cast  or  crucible  steel  and  in  manufacture 
pass  through  the  successive  processes  of  forging,  annealing,  grinding, 
cutting,  hardening,  and  tempering.  They  have  three  distinguishing 
features— length,  kind  or  name,  and  cut  or  coarseness  of  teeth. 
Length  is  measured  from  the  heel  A  to  the  point  B,  Fig.  48,  the  tang 
C  not  being  included.  These  lengths  vary  from  3  inches  to  20  inches. 

Classification  of  Style  and  Cuts.  There  are  many  kinds  of  files 
manufactured.  Those  in  common  use  are  shown  in  section  in  Fig.  49 


MACHINE  SHOP  WORK 


29 


as  follows:  A — flat  file;  B — hand  file;  C — warding  file;  D — square 
file;  E — three  square  or  triangular  file;  F — half  round  file;  and 
G — round  file. 

The  cut  of  files  is  in  two  styles — single  and  double;  and  each 
style  has  several  grades  of  coarseness,  viz,  coarse,  bastard,  second- 


R 


Fig.  49.     Cross-Section  of  Files 

cut,  smooth,  and  dead  smooth.  The  last  two  grades  are  some- 
times called  fine  and  superfine.  As  is  shown  in  Fig.  50,  the  coarse- 
ness of  each  style  varies  with  the  length — the  longer  the  file  the 
coarser  the  cut. 

Convexity  of  Files.     If  the  cutting  surface  of  a  file  were  perfectly 
flat,  the  number  of  teeth  or  cutting  points  engaged  with  the  work 
would  depend  on  both  the 
width  of  the  file  and  the 
width  of  the  piece  being  filed. 
To  force    as  many  cutting 
points  as  would  be  contained 
in  such  a  large  area  deeply 
enough   into  the   metal  to 
enable   each  to  remove  its 

share  of  the  stock  would  be  beyond  the  power  of  the  man  pushing 
the  file.  To  avoid  this  necessity  for  great  pressure,  files  are  usually 
"bellied"  or  made  slightly  convex  in  the  direction  of  their  length,  so 
that,  theoretically,  the  file  and  the  work  are  in  contact  only  on  a 
line  as  long  as  the  width  of  the  file.  This  enables  the  file  to  be 
forced  into  the  metal  sufficiently  for  the  teeth  to  bite,  and  thus 
avoids  dulling  the  teeth,  which  always  occurs  when  the  file  is 
allowed  to  glide  over  the  work  without  sufficient  cutting. 


Fig.   50.     Diagram  Showing  Coarseness  of  Files 


30 


MACHINE  SHOP  WORK 


This  convexity  of  files  also  serves  another  purpose.  The  pres- 
sure applied  to  the  file  to  make  it  bite  bends  the  file  more  or  less, 
Fig.  51,  and  if  the  file  in  its  natural  state  were  perfectly  flat,  when 
cutting  it  would  be  concave;  and  this  would  prevent  the  production 


Fig.  51.     Bench  Filing 

of  a  flat  surface  as  it  would  cut  away  at  the  edges  of  the  work,  leav- 
ing a  convex  surface.  Such  files  might,  however,  be  used  on  convex 
surfaces. 

Height  of  Work  for  Different  Classes  of  Files.     Work  for  filing 
is  usually  held  in  a  vise,  and,  under  ordinary  circumstances,  the 


Fig.  52.     Special  File  Holder 


surface  of  the  work  should  be  about  the  height  of  the  elbow.  For 
fine  work  with  small  files,  where  close  observation  is  of  more  impor- 
tance than  pressure  on  the  file,  the  work  should  be  higher  than  this, 


MACHINE  SHOP  WORK 


31 


the  height  increasing  with  the  refinement  of  the  work.  On  the 
other  hand,  for  very  heavy  filing,  where  great  pressure  is  absolutely 
necessary,  the  work  should  be  several  inches  below  the  point  of  the 
elbow,  so  that  the  weight  of  the  body  may  be  used  to  good  advantage, 
and  also  because  the  workman  naturally  stoops  a  little  when  exert- 
ing a  great  pressure  on  the  file. 

File  Handles.  The  handles  commonly  attached  to  files  are  of 
wood  and  are  made  to  fit  the  hollow  of  the  hand.  The  handle  is 
driven  onto  the  tang  of  the  file,  a 
ferrule  on  the  handle  preventing 
it  from  splitting.  Care  should  be 
taken  to  have  the  axis  of  the 
handle  parallel  with  the  file.  A 
good  way  to  prepare  the  handle  for 
the  tang  is  to  heat  the  tang  to  a 
dull  red,  the  file  proper  being  kept 
cool  by  a  piece  of  wet  cotton  waste, 
and  the  hole  in  the  handle  burned 
out  until  the  tang  is  almost  in  the 
position  it  is  designed  to  finally 
occupy.  After  cooling  the  tang, 
very  little  driving  will  be  required 
to  securely  fasten  the  handle  to 
the  file. 

When  filing  surfaces  of  such 
size  that  the  handle  as  ordinarily 
applied  would  interfere  with,  the 
use  of  the  file,  the  tang  may  be 
bent  up  to  an  angle  so  that  the 
handle  will  clear  the  surface.  Various  forms  of  holders  are  used 
for  filing  under  these  circumstances,  the  simplest  forms  being  shown 
in  Fig.  52. 

Correct  Filing  Position.  The  correct  position  for  filing  is  about 
as  follows :  feet  about  8  inches  apart  and  at  right  angles,  the  left  foot 
being  in  line  with  the  file;  stand  back  from  the  vise  so  that  the  body 
may  follow  the  file  slightly;  grasp  the  file  handle  with  the  right  hand, 
fingers  below,  thumb  on  top  of,  the  handle.  For  coarse  filing,  place 
the  ball  of  the  thumb  of  the  left  hand  on  the  point  of  the  file,  and  for 


Fig.  53.     Bench  Filing  Position 


32  MACHINE  SHOP  WORK 

fine  filing  grasp  the  point  of  the  file  with  the  thumb  and  forefinger 
of  the  left  hand,  Fig.  53.  When  holding  the  file  in  one  hand,  as  is 
often  done  in  light  work,  the  forefinger  should  be  on  top  of  the  file, 
pointing  in  the  direction  of  its  length,  as  is  shown  in  Fig.  54.  This 
allows  free  movement  of  the  hand  and  wrist,  pressure  being  applied 
principally  by  the  forefinger. 

As  file  teeth  or  cutting  edges  point  toward  the  end  of  the  file, 
it  is  evident  that  the  file  can  cut  only  when  moving  in  a  forward 
direction.  On  the  return  stroke,  the  pressure  should  be  relieved; 
otherwise  the  teeth  will  be  dulled  when  drawn  back  over  the  surface. 

Choice  of  Files  Depends  on  Work.  The  kind  of  metal  being 
worked  determines  in  a  great  measure  the  character  of  the  file  to  be 
used.  Cast  iron,  especially  if  the  scale  has  not  been  previously 
removed,  is  particularly  hard  on  a  new  file,  as  the  glassy  character 


Fig.  54.     Position  for  Single  Hand  Filing 

of  the  scale  tends  to  dull  the  cutting  edges.  New  files  should  never 
be  used  on  such  a  surface.  It  is  found  that  on  tool  steel,  and  on  hard 
materials  generally,  a  second-cut  file  is  better  than  the  bastard. 
This  is  because  if  pressure  enough  is  exerted  to  cause  the  coarse 
teeth  of  the  bastard  to  bite  into  the  work,  the  teeth,  being  com- 
paratively long,  are  very  likely  to  be  broken  off.  In  the  second-cut 
file,  the  teeth  are  shorter  and  present  more  cutting  points  in  a  given 
area,  thus  preventing  excessive  duty  being  imposed  on  a  few  teeth. 

Softer  metals,  such  as  brass  and  bronze,  allow  the  use  of  the 
coarser  grades. 

Cleaning  File.  The  particles  of  metal  removed  by  a  file  fre- 
quently remain  in  the  teeth  and  diminish  their  cutting  qualities. 
In  the  case  of  hard  metals,  these  particles,  or  "pins",  often  scratch 
the  work.  It  is  necessary,  therefore,  that  files  be  frequently  cleaned. 
This  may  be  done  in  a  measure  by  striking  the  edge  of  the  file  lightly 


MACHINE  SHOP  WORK 


33 


against  the  bench  or  vise,  but  it  is  more  effectually  performed  by 
using  a  stiff  brush  or  a  piece  of  card  clothing,  Fig.  56.  In  the  finest 
grades  of  files,  a  thin  piece  of  wood  or  sheet  brass  may  be  drawn 
across  the  surface  of  the  file  as  shown  in  Fig.  55,  and  the  filings  are 
removed  by  the  points 
extending  into  the  file 
teeth. 

When  filing  cast 
iron,  neither  the  file  nor 
the  work  should  be 
allowed  to  become  greasy, 
as  this  tends  to  make 

the     file      Slide     without  Fig.  55.     Removing  Pins  from  a  File 

cutting.     In  filing  steel, 

however,  if  the  file  be  oiled  or  filled  with  chalk,  the  pinning  of 
the  file  is  prevented  in  a  large  degree,  and  frequent  use  of  the  card 
or  brush  is  not  necessary. 

Draw  Filing.  What  is  known  as  draw  filing  is  done  by  grasping 
the  file  at  each  end  and  moving  it  sidewise  across  the  work,  Fig.  57. 
The  amount  of  stock  removed  by  this  process  is  usually  very  small, 
the  object  being  to  lay  the  file  marks  parallel  to  the  length  of  the 
work.  For  draw  filing,  single-cut  files  are  better  than  double-cut 
as  they  are  less  likely  to  scratch  the  work.  The  remarks  concerning 
cleaning,  oiling,  and  chalking  apply  both  to  cross  filing  and  draw 
filing. 

Polishing.  No  matter  how  carefully  filing  is  done,  it  does  not 
leave  a  surface  that  is  pleasing  to  the  eye;  the  file  marks  are  more  or 


Fig.  56.    File  Brush 

less  irregular  and  the  whole  surface  is  dull.  Exposed  parts  of 
machines  which  are  not  painted  are  usually  polished.  Polishing 
does  not  necessarily  improve  the  surface,  but  simply  brightens  it 
and  renders  it  more  attractive.  As  a  rule,  a  polished  surface  is  not 
a  true  surface,  no  care  being  taken  to  maintain  its  trueness.  In 


34  MACHINE  SHOP  WORK 

ordinary  machine  work,  polishing  is  usually  done  by  abrasives,  such 
as  emery,  corundum,  and  carborundum;  while  rouge,  crocus,  rotten- 
stone,  and  tripoli  are  used  on  fine  work,  especially  on  brass  and 
composition.  Emery,  for  example,  is  crushed  and  sorted  into 
grades  varying  from  No.  8  to  flour,  the  number  of  the  grade  indi- 
cating the  number  of  meshes  per  linear  inch  in  the  sieve  used  in 
sorting.  These  grades  sometimes  bear  arbitrary  designations,  No.  1 
indicating  a  coarse  grade  and  Nos.  0,  00,  000,  0000  showing  the  finer 
grades. 

Methods  of  Using  Powders  and  Cloths.    Emery  powders  are 
sometimes  mixed  with  oil  and  applied  directly  to  the  work  by 


Fig.  57.     Draw  Filing 

wooden  blocks  or  clamps;  but  the  more  .common  method  is  to  use 
'what  is  known  as  emery  cloth,  the  grains  being  glued  to  a  strong  cloth 
backing.  The  finer  grades  are  used  on  paper  in  the  same  manner. 
Emery  cloth  is  used  in  many  ways — it  may  be  wrapped  around 
a  file;  folded  or  tacked  to  a  block  of  wood;  glued  to  wooden  sticks 
about  15  in.  X  li  in.  X  \  in.,  fastened  around  rollers  for  internal 
curves,  or  glued  to  wooden  or  steel  discs  and  rotated  in  a  lathe  or 
special  machine.  In  all  cases  the  object  is  to  grind  down  the  sur- 
face, using  a  sufficient  number  of  grades  of  cloth  to  produce  the 
degree  of  polish  desired.  The  marks  are  laid  parallel  to  each  other, 
making  what  is  known  as  a  "grain".  When  the  process  is  to  be 
carried  to  such  an  extent  that  no  grain  is  to  be  visible,  the  finer 


MACHINE  SHOP  WORK 


35 


polishing  agents  are  used,  usually  applied  with  a  cloth  wheel  or 
"lap".  Old  cloth  does  finer  work  than  new,  and  oil  on  the  cloth  will 
make  a  finer  cut. 

Hand  Scraping.  When  two  flat  or  curved  surfaces  are  to  be 
worked  together,  and  close  contact  over  the  surfaces  of  both  is 
desired,  they  are  hand  scraped.  Scraping  removes  less  metal  than 
filing  and  also  enables  the  workman  to  confine  the  removal  to  limited 
areas.  The  scraper,  which  should  be  made  from  a  very  close- 
grained  tool  steel,  is  nearly  2  feet  long  exclusive  of  the  handle.  The 
general  shape  is  shown  in  the  upper  view  of  Fig.  58.  The  cutting 
edge  is  about  ^  of  an  inch  thick  and  If  inches  wide.  It  is  ground 
on  an  emery  wheel  or  grindstone  and  carefully  oilstoned,  leaving  the 
cutting  edge  as  straight  as  possible.  Scrapers  are  sometimes  made 
from  old  files,  the  teeth  being  ground  off  and  the  end  drawn  out 


ih. 


Fig.  58.     Straight  and  Bent  Hand  Scrapers 

wide  and  thin.  Sometimes  the  end  is  bent  at  right  angles  to  the 
shank,  as  shown  in  the  lower  view  of  Fig.  58.  The  cutting  done  by 
scrapers  should  be  perfectly  smooth  and  free  from  scratches. 

Testing  Plane  Surfaces.  In  using  the  surface  plate  as  a  test  for 
the  trueness  of  a  plane,  such  as  a  valve  or  its  seat,  the  plate  is 
covered  with  a  very  thin  coating  of  red  lead  and  then  rubbed  over 
the  valve  or  seat.  The  latter  should  have  previously  been  finished 
as  smoothly  as  possible.  The  spots  where  the  red  lead  shows  contact 
are  scraped  off  and  the  process  continued  until  contact  over  the 
entire  surface  is  obtained.  During  the  last  part  of  the  operation, 
alcohol  should  be  used  instead  of  red  lead,  as  it  leaves  clean  bright 
spots  to  indicate  where  the  scraper  must  be  applied.  Small  pieces 
of  work  are  rubbed  over  the  surface  plate,  and  in  any  case  care 
should  be  taken  to  distribute  the  wear  uniformly  over  the  plate  in 
order  to  prolong  the  trueness  of  the  plane.  The  scraper  for  concave 


36 


MACHINE  SHOP  WORK 


surfaces,  such  a*s  bearings,  is  of  the  general  shape  of  a  half-round  file 
without  teeth.     In  such  cases,  the  spindle  itself  takes  the  place 

of  a  surface  plate.  The  method  of 
holding  and  using  such  a  scraper  is 
shown  in  Fig.  59. 

Scraping  for  Finish  Only. 
Scraping  is  sometimes  done  as  a 
matter  of  finish,  and  not  for  the 
purpose  of  getting  an  accurate  sur- 
face. It  is  then  termed  "spotting". 

i      >.  s       v  A  spotted  surface,  therefore,  does 

^  ^       not  always  indicate  accuracy.  Many 

machine  parts  can  be  more  cheaply 
finished  by  scraping  than  by  polishing. 


Fig.  59.     Scraping  Spindle  Bearing 

HAND  PUNCHES 

Prickpunch.  .The  prickpunch,  Fig.  60,  is  made  of  tool  steel 
with  a  hardened  conical  point  of  about  60  degrees.  It  is  about  3J 
inches  long  and  i  inch  in  diameter.  It  is  used  for  making  very  small 
indentations  at  intervals  on  a  line,  or  at  intersections  of  lines. 

Center  Punch.  The  center  punch,  also  shown  in  Fig.  60,  is 
made  of  the  same  general  appearance  as  the  prickpunch,  but  is 


Fig.  60.     Hand  Punches.     Forged  Center  Punch  Above;  Prickpunch  Below 

about  5  inches  long,  |  inch  in  diameter,  and  has  a  point  angle  of 
about  90  degrees.  The  principal  use  of  this  punch  is  to  make  center 
holes,  marking  the  centers  on  the  ends  of  pieces  to  be  turned. 

Ordinary  forged  center  punches  are  usually  made  of  hexagonal 
steel;  but  if  round  stock  is  used,  the  grip  should  be  fluted  or  knurled 
to  prevent  slipping  in  the  fingers. 


MACHINE  SHOP  WORK 


37 


Scratch  Awl.  The  scriber  or  scratch  awl,  Fig.  61,  is  made  in 
many  forms,  but  consists  essentially  of  a  cast-steel  rod  about  8 
inches  long  and  -f^  inch  in  diameter,  with  a  long,  slender,  hardened 


Fig.  61.     Forms  of  Scribers 
Courtesy  of  L.  S.  Starrelt  Company,  Athol,  Massachusetts 


point  at  each  end.  Frequently  one  point  is  bent  at  right  angles  to 
the  shank.  As  the  name  indicates,  this  tool  is  used  for  marking 
lines  on  the  surface  of  metal. 

TEMPLETS 

Where  the  same  lay-out  is  to  be  many  times  repeated,  templets 
are  used.  This  method  avoids  the  necessity  of  making  measure- 
ments in  the  laying  out  of  the  work. 

Marking  Templet.  The  marking  templet  consists  of  a  piece 
of  the  same  shape  as  the  finished  article.  It  is  usually  laid,  on  a  flat 


Fig.  62.     Steel  Clamps 


surface  and  held  fast  by  iron  clamps  as  shown  in  Fig.  62.  The  out- 
line is  then  marked  on  the  surface  with  a  scriber  and  sometimes 
emphasized  by  prickpunch  marks. 


38  MACHINE  SHOP  WORK 

Filing  Templet.  The  filing  templet  is  of  the  same  character  as 
the  marking  templet  except  it  is  hardened.  It  is  clamped  in  the 
vise  with  the  piece  to  be  shaped,  and  the  surface  filed  down  to  coin- 
cide with  the  form  of  the  templet. 

Jigs.  Where  holes  are  to  be  drilled  in  duplicate,  a  templet 
known  as  a  plate  jig  is  used.  These  are  made  so  that  they  'fit  over 
the  piece  to  be  drilled  and,  when  clamped  in  position,  indicate  the 
location  of  the  holes  by  means  of  hardened  steel  bushings  set  in  the 
templet. 

The  making  of  templets  and  jigs  is  one  of  the  finest  branches  of 
the  machinist's  work  and  is  generally  classed  under  the  head  of  "Tool- 
Making".  The  rapid  and  economical  production  of  machine  parts 
in  quantity  depends  largely  on  the  tool-maker,  who  must,  therefore, 
be  considered  the  highest  type  of  machinist. 

DRILLING 

Drilling.  Drilling  is  the  term  used  by  shop  men  to  denote  hole 
production  by  means  of  a  rotating  tool  which  is  provided  with 
cutting  edges  located  at  its  point.  The  drill,  therefore,  is  an  end 
cutting  tool  as  distinguished  from  the  ordinary  reamer  which  usually 
cuts  on  its  sides. 

Types  of  Drills 

Flat  Drills.  Drills  are  of  two  general  classes,  the  flat  and  the 
twist.  A  flat  drill  of  a  common  type  is  shown  in  Fig.  63.  The 
angle  between  the  two  cutting  edges  should  be  about  110  degrees. 
These  drills  are  usually  made  from  round  tool  steel  drawn  out  wide 
and  thin,  as  shown,  the  undressed  end  being  used  for  holding.  The 
flat  drill  is  usually  made  in  the  shop  where  it  is  to  be  used.  Its  low 
first  cost  is  the  principal  reason  for  its  existence. 

Flat  Chucking  Drill.  Flat  drills  made  from  thin  flat  stock  are 
used  in  connection  with  a  slotted  rest  to  start  and  enlarge  previously 
cored  holes  in  lathe  chuck  work.  They  are  called  chucking  drills. 
The  end  of  the  shank  of  the  drill  is  provided  with  a  center  hole  to 
receive  the  dead  center  of  the  machine.  The  drill  and  rest  are 
shown  in  Fig.  64. 

Twist  Drills.  The  simplest  form  of  twist  drill  is  cylindrical 
throughout  its  entire  length,  as  shown  in  Fig.  65,  and  has  two  spiral 
flutes  which  at  the  end  serve  to  form  the  cutting  lips,  and  which  also 


MACHINE  SHOP  WORK 


39 


serve  to  carry  the  chips  from  the  hole.  The  included  angle  of  the 
lips  is  118  degrees.  The  twist  drill  will  work  more  accurately  than 
the  flat  drill,  as  the  cylindrical  portion  serves  as  a  guide  to  keep  the 
cutting  lips  in  their  proper  position.  The  edges,  being  somewhat 


Fig.  63.     Blacksmith's  Drills 

hooking,  removes  the  metal  by  a  cutting  instead  of  a  scraping  action 
as  in  the  flat  drill.  This  form  of  drill  not  only  can  be  fed  faster  but 
can  be  forced  into  the  work  with  less  power,  as  it  has  a  tendency, 
especially  noticeable  in  soft  metals,  to  feed  itself  into  the  work. 
Straight  shank  twist  drills 
are  made  from  .0135  inch  to 
2J  inches  in  diameter;  the 
smaller  sizes  are  sold  in  sets 
designated  by  the  numbers  1 
to  80;  by  the  letters  A  to 
Z;  or  by  the  fractional  sizes 
$  inch  to  YQ  inch. 

Tapered  Shanks.      The 
taper-shank    twist    drill    is  Fig.  64.   chucking  DHH  Rest 

shown  in  Fig.  66.     It   con- 
sists of  a  body  A,  which  is  fluted  and  does  the  actual  work,  and 
a  taper  shank  B,  by  which  it  is  held.    This  taper  fits  accurately 
into  the  spindle  or  chuck  of  the  drill  press.     At  the  end  there  is  a 
tongue  C,  which  slips  into  the  keyway  in  the  spindle  or  chuck.    As 


40 


MACHINE  SHOP  WORK 


this  surface  is  flat,  it  serves  as  a  bearing  by  which  the  drill  is  driven. 
This  relieves  the  tapered  portion  from  the  stress  of  driving  by  fric- 
tional  resistance  alone.  For  small  drills  this  frictional  resistance  is 
sufficient,  but  for  larger  sizes  it  will  not  do  at  all.  If  for  any  reason 
the  tongue  should  become  broken,  no  dependence  should  be  placed 
upon  the  frictional  resistance  of  the  taper  shank  to  drive  the  drill. 


Fig.  65.     Typical  Twist  Drill 
Courtesy  of  Union  Twist  Drill  Company,  Athol,  Massachusetts 

The  drill  will  slip  and  wear  the  socket,  which  will  become  enlarged 
and  make  a  misfit  for  other  drills. 

The  standard  taper  for  drill  shanks,  known  as  the  Morse,  is 
|  inch  to  the  foot.  There  is  another  standard  taper,  known  as  the 
Jarno,  which  has  a  taper  of  -fu  inch  to  the  foot.  No  attempt  should 
be  made  to  run  the  drills  of  one  taper  in  the  sockets  of  the  other. 


Fig.  66.     Taper  Shank  Twist  Drill 
Courtesy  of  Morse  Twist  Drill  Company,  New  Bedford,  Massachusetts 

A  flat  taper  key,  or  drift,  introduced  into  the  keyway,  engages 
the  end  of  the  tongue  and  serves  to  remove  the  drill  from  the  spindle. 

Farmer  Drills.  Drills  of  cylindrical  form  are  also  made  with 
straight  flutes  as  shown  in  Fig.  67.  They  are  used  for  drilling  soft 
metals,  such  as  brass,  especially  when  the  drill  passes  entirely  through 


Fig.  67.     Straightway  or  Straight  Fluted  Drill 
Courtesy  of  Union  Twist  Drill  Company,  Athol,  Massachusetts 

the  piece.  As  it  breaks  through  the  metal,  a  drill  with  spiral  flutes 
tends  to  draw  itself  through  rapidly,  as  if  it  were  a  screw  working 
in  a  nut.  This  may  break  the  drill  or  move  the  work  from  positior. 
Straight  flutes  give  the  same  cutting  action  as  a  flat  drill  and  avcid 
the  tendency  to  draw. 


, 
MACHINE  SHOP  WORK  41 

Care  of  Drills 

Lubrication  of  Drills.  When  drilling  tougn  metals,  such  as 
steel  and  wrought  and  malleable  iron,  heat  is  generated  by  the 
bending  or  changing  of  the  form  of  the  metal  being  removed  and  by 
friction  caused  by  the  chips  moving  over  the  lips  of  the  drill.  The 
heating  is  similar  to  the  heating  of  a  piece  of  wire  bent  quickly  back 
and  forth.  As  there  is  danger  of  heating  the  drill  to  a  temperature 
that  will  draw  the  temper  and  soften  the  drill,  plenty  of  lard  oil,  or  a 
mixture  of  potash  and  water,  should  be  used.  This  is  not  so  much 
for  lubrication  as  to  conduct  away  the  heat. 

Copper  is  the  most  difficult  to  drill  of  all  the  common  metals  on 
account  of  its  extreme  toughness;  then,  too,  copper  heats  to  a  higher 
temperature  on  account  of  its  low  specific  heat.  Brass  does  not 
require  the  use  of  oil,  and  cast  iron  is  usually  drilled  dry. 


Fig.  68.     Oil  Tube  Drill 
of  Cleveland  Twist  Drill  Company,  Cleveland,  Ohio 

As  the  heat  is  produced  at  the  point  of  the  drill,  it  is  desirable, 
particularly  in  the  case  of  deep  holes,  that  the  oil  be  applied  directly 
at  the  drill  point.  For  this  purpose,  oil-tube  drills,  such  as  shown 
in  Fig.  68,  are  used.  The  oil  is  supplied  under  pressure,  and  not 
only  removes  the  heat  but  also  carries  away  the  chips. 

Speed  of  Drills.  The  speed  at  which  drills  should  be  rotated 
depends  both  on  the  diameter  of  the  drill  and  on  the  material  oper- 
ated upon.  No  absolute  rule  can  be  given  for  any  one  metal  or 
diameter  of  drill  because  of  the  variation  in  hardness  and  tenacity  of 
the  material  and  the  condition  of  the  cutting  edges  of  the  drill.  The 
operator  must  exercise  his  own  judgment. 

Table  I,  giving  the  speed  of  drills  in  revolutions  per  minute,  is 
based  on  a  peripheral  speed  of  30  feet  a  minute  for  mild  steel,  35 
feet  per  minute  for  cast  iron,  and  60  feet  per  minute  for  brass,  using 
carbon  tool  steel  drills. 

The  rate  of  feed  also  depends  on  the  drill  diameter  and  on 'the 
material.  The  Cleveland  Twist  Drill  Company  gives,  as  a  maxi- 
mum, one  inch  of  feed  for  95  to  125  revolutions. 


42 


MACHINE  SHOP  WORK 


TABLE  I* 
Speed  of  Drills 


DIAMETER 
OF  DRILL 

SOFT  STEEL 
OR  WROUGHT  IRON 
(r.  p.  ni.) 

CAST  IRON 
(r.  p.  m.) 

BRASS 
(r.  p.  m.) 

A 

1824 

2128 

3648 

| 

912 

1064 

1824 

608 

710 

1216 

I 

456 
365 

532 
425 

912 
730 

I 

304 

355 

608 

280 

304 

520 

.  ! 

228 
203 

226 
236 

456 
405 

A 

16 

182 
166 

213 

194 

665 
332 

i 

152 

177 

304 

H 

140 

164 

280 

I 

130 

152 

260 

15 
T6 

122 

142 

243 

1 

114 

133 

228 

IP 

108 

125 

215 

102 

118 

203 

1^ 

96 

112 

192 

H 

91 

106 

182 

IP 

87 
83 

101 
97 

174 
165 

1A 

80 

93 

159 

li 

76 

89 

152 

If 

73 

70 

85 

82 

145   V 
140 

ITS' 

68 

79 

135 

1? 

65 

76 

130 

IT£ 

63 

73 

125 

1- 

60 

71 

122 

IT! 

59 

69 

118 

2 

57 

67 

114 

Resharpening  Drills.  Great  care  should  be  exercised  in  the 
resharpening  of  drills.  The  cone  point  of  a  drill  should  be  symmetri- 
cal, that  is,  the  lips  should  be  of  the  same  length  and  form  the  same 
angle  with  the  axis.  If  the  lips  are  of  unequal  length,  the  hole  will 
be  larger  than  the  drill,  as  is  shown  in  Fig.  69.  The  point  is  not  in 
the  axis,  and  the  hole  will  not  only  be  large  but  also  will  not  be 
parallel  to  the  drill  spindle.  If  the  lips  do  not  form  equal  angles 
with  the  axis,  all'  the  cutting  will  devolve  upon  the  one  making  the 
greater  angle,  as  shown  in  Fig.  70.  Such  a  drill  will  not  cut  as 
fast  as,  and  will  become  dull  sooner  than,  one  which  is  properly 
ground. 

*Courtesy  of  Cleveland  Twist  Drill  Company. 


MACHINE  SHOP  WORK 


43 


Hand-grinding,  especially  of  twist  drills,  is  neither  accurate 
nor  satisfactory;  it  is  much  better  to  do  such  work  on  a  regular  drill 
grinder  built  especially  for  the  purpose. 


Fig.  69.     Drill  with  Lips  of 
Unequal  Length 


Fig.  70.     Drill  with  Lips  of 
Unequal  Angles 


When  resharpening  carbon  tool  steel  drills,  care  must  always 
be  exercised  that  the  cutting  edges  are  not  overheated  on  the  stone 
or  emery  wheel.     If  overheated,  the  temper  will  be  drawn  and 
the  drill  become  too  soft  to 
properly  do  its  work.    The     " 
clearance    angle    is    also  of 
extreme    importance.     This 
should    be    12    degrees,    as 
shown  in  Fig.  71 .    If  the  drill 
lips  are  not  .properly  cleared 
or  backed  off,  the  drill  must 

Crush.  Fig.  71.     Cutting  Edge  Clearance 

REAMERS 

Use  of  Reamers.  It  is  difficult,  if  not  quite  impossible,  to  drill 
a  hole  to  an  exact  standard  diameter.  For  much  work,  a  variation 
of  a  few  thousandths  of  an  inch  from  the  nominal  diameter  is  of  no 
account.  Where  greater  accuracy  than  this  is  required,  the  holes 
are  reamed,  that  is,  the  hole  is  first  drilled  somewhat  smaller  than  it 
is  desired  and  is  then  reamed  out  to  the  proper  size  with  a  reamer. 


44 


MACHINE  SHOP  WORK 


Holes  drilled  with  common  chucking  drills  are  usually  y^  inch 
under  the  finish  size.  A  chucking  reamer,  Fig.  72,  is  used  to 
enlarge  the  hole  to  within  about  .005  inch  of  the  true  size.  This 
reamer  is  centered  on  both  ends  and  turned  to  size.  The  entering 


Fig.  72.     Flat  Chucking  Reamer 

end,  which  does  the  cutting,  is  given  a  short,  sharp  taper,  while  the 
straight  portion  serves  as  a  guide  to  keep  the  tool  in  position.  By 
this  means,  the  drilled  hole  is  straightened  and  brought  close  to  size. 

Hand  Reaming.  To  give  the  hole  a  smooth  surface  and  a  cor- 
rect diameter,  a  fluted  hand  reamer,  of  which  there  are  various  forms, 
is  used.  This  tool  is  not  intended  to  remove  large  amounts  of 
metal,  but  serves  only  to  increase  the  size  of  a  hole  by  a  small  frac- 
tion of  an  inch  up  to  the  diameter  required.  The  hole  should  not 
be  more  than  0.007  inch  smaller  than  the  hand  reamer.  It  is  evident 
that  if  the  reamer  were  to  be  made  of  the  same  diameter  throughout 
its  whole  length,  it  would  be  very  difficult  to  make  it  enter  the  hole. 
In  order  to  facilitate  this,  it  is  usually  made  slightly  tapering  for  a 
distance  from  the  entering  end  equal  to  about  one  diameter. 

One  form  of  reamer  has  a  shallow  screw  thread  cut  at  the  enter- 
ing end.  This  thread  takes  hold  of  the  metal  and  draws  down  into 
the  work.  When  using  a  reamer,  it  is  always  well  to  pass  the  entire 


Fig.  73.     Solid  Hand  Reamer 

tool  through  the  hole.  The  leading  end  is  subjected  to  the  greatest 
amount  of  wear  because  it  does  the  greatest  amount  of  work.  If, 
therefore,  only  the  leading  end  is  put  through,  the  hole  will  not  be 
of  a  uniform  diameter  throughout.  Oil  should  always  be  used  on 
reamers  when  they  are  working  in  wrought  iron  or  steel. 

The  hand  reamer,  Fig.  73,  is  the  typical  form,  and  one  which 
can  be  used  in  many  cases  in  place  of  special  forms.    Fig.  74  is  better 


MACHINE  SHOP  WORK 


45 


adapted  for  use  in  the  lathe  than  the  hand  reamer.    This  may 
follow  the  chucking  reamer  to  finally  finish  a  hole. 

In  reaming  cored  holes,  the  cylindrical  chucking  reamer,  some- 
times called  a  roughing  reamer,  is  often  used.     It  is  made  either 


Fig.  74.     Plain  Shell  Reamer 

Courtesy  of  Brown  and  Sharpe  Manufacturing 

Company,  Providence,  Rhode  Island 


Fig.  75.     Rose  Shell  Reamer 

Courtesy  of  Brown  and  Sharpe  Manufacturing 

Company,  Providence,  Rhode  Island 


rose,  Fig.  75,  fluted,  or  with  three  spiral  flutes,  Fig.  76,  and  generally 
has  solid  shanks.  The  last-named  style  will  finish  very  smooth  and 
close  to  size  when  started  true  by  preliminary  boring. 


Fig.  76.     Spiral  Chucking  Reamer  Drill 

A  solid  reamer  cannot  be  sharpened  without  reducing  its  diam- 
eter; therefore,  it  must  be  used  carefully  in  order  to  prolong  its  life. 
Reamers  with  adjustable  blades  meet  this  objection,  but  cost  much 


Fig.  77.    Expanding  Reamer  and  Arbor 

more  than  the  solid  form.  An  expanding  reamer,  Fig.  77,  can  be 
slightly  enlarged  to  compensate  for  grinding  and  is  then  used  as  a 
solid  reamer.  Fig.  78  shows  an  adjustable  reamer  with  inserted 
blades. 


46 


MACHINE  SHOP  WORK 


Taper  Reamers.  Reamers  are  made  for  tapered  as  well  as  for 
straight  holes.  The  angle  varies  with  the  intended  use  of  the  taper. 
For  example,  the  locomotive  taper  of  y^  inch  per  foot  is  intended  for 
bolt  holes  where  plates  are  to  be  drawn  solidly  together  and  the 


Fig.  78.     Reamer  with  Inserted  Blades 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  Island 

holes  completely  filled.  It  is  very  difficult  to  remove  a  bolt  from  a 
hole  with  such  a  slight  taper.  When  pieces  are  pinned  together, 
such  as  a  hub  to  a  shaft,  it  is  intended  that  they  can  be  separated 
when  desired,  so  the  taper  is  made  steeper,  generally  J  inch  per  foot. 


Fig.  79.     Types  of  Taper  Reamers 

This  has  come  to  be  known  as  the  pin  taper.  Taper  holes  for  holding 
lathe  centers  and  taper  shank  twist  drills  are  generally  made  f  inch 
per  foot — the  Morse  taper.  This  angle  holds  the  tool  firmly,  and  still 
it  can  be  easily  removed.  The  three  tapers  mentioned  are  recog- 
nized as  standard,  and 
reamers  for  them  are  car- 
ried in  stock.  Of  course 
many  other  tapers  are  used 
by  different  manufacturers, 
but  they  are  regarded  as 

Fig.  80.    Method  of  Stepping  Holes  before  Using  Special.     Fig.  79  shoWS  taper 

Taper  Reamer 

reamers. 

Taper  reamers  differ  from  hand  reamers  only  in  the  angle  and 
by  not  requiring  the  tapered  entering  end. 

Holes  to  be  reamed  by  taper  reamers  must  be  slightly  larger 
than  the  small  end  of  the  reamer;  and,  if  the  hole  is  deep,  it  is  usual 


MACHINE  SHOP  WORK 


47 


to  make  a  stepped  hole,  shown  exaggerated  in  Fig.  80,  by  using 
drills  of  different  diameters. 

When  not  carefully  sharpened,  all  forms  of  reamers  have  a 
tendency  to  chatter  and  produce  rough  surfaces.  To  avoid  this, 
the  flutes  are  frequently  irregularly  spaced;  another  method  is  to 
use  spiral  flutes,  usually  left  hand. 

HAND  THREADING  TOOLS 
Taps 

Types  of  Taps.  When  internal  thread  cutting  is  done  by  hand, 
the  tool  used  is  called  a  tap.  There  are  many  styles  of  taps,  the 


Fig.  81.     Types  of  Hand  Taps:     Left — Taper  Tap;  Centei 

Tap;  Right — Bottoming  Tap 

Courtesy  of  Wiley  and  Russell  Manufacturing  Company, 
Greenfield,  Massachusetts 


-Plug 


names  in  some  cases  being  suggested  from  the  shape,  but  more  often 
from  the  use.  In  most  machine  shops  are  found  the  following 
forms:  hand,  machine  screw,  pipe,  pulley,  stay-bolt,  boiler,  and 
tapper;  of  these  the  hand  and  machine  screw  are  the  most  common. 
The  object  of  all  is  to  make  helical  grooves,  called  threads,  in  holes, 
so  that  they  may  receive  and  hold  screws,  bolts,  studs,  etc. 

Size  of  Drill  for  Tapped  Hole.    As  the  size  of  a  tap  is  the  out- 
side diameter  of  its  threads,  it  is  evident  that  the  hole  drilled  for 


48 


MACHINE  SHOP  WORK 


TABLE  II 
Taps  and  Corresponding  Drills 


TAP 

DIAMETER 
(in.) 

No. 
THREADS 
(per  in.) 

u.  s. 

STANDARD 
DRILL 
DIAMETER 
(in.) 

V-THREAD 
DRILL 
DIAMETER 
(in.) 

TAP 
DIAMETER 
(in.) 

No. 
THREADS 
(per  in  ) 

u.  s. 

STANDARD 
DRILL 
DIAMETER 
(in.) 

V-THREAD 
DRILL 
DIAMETER 
(in.) 

1 

20 

A 

11 

If 

5 

If 

JH 

A 

18 

I 

H 

2 

41 

Iff 

f« 

1 

16 

& 

2| 

4| 

1H 

i| 

A 

14 

IT 

IT 

2J 

4 

I 

13 

T§ 

If 

2| 

4 

2^ 

2^3- 

A 

12 

A 

A 

3 

3| 

21 

2j 

H 

11 
11 

3| 

If 

2| 
3} 

2! 
2H 

f 

10 

• 

iir 

s| 

3* 

3  A 

ft 

10 

|i 

H 

4 

3 

3A 

3^ 

9 

ft 

If 

4? 

2i 

31  3 
16 

3H 

if 

9 

1 

If 

41 

4 

3| 

1 

8 

H 

It 

4| 

2j 

4£ 

4J- 

U 

7 

if 

5 

21 

4| 

41 

H 

7 

1A 

1^2 

51 

21 

4| 

41 

if 

6 

IA 

if 

5| 

2 

,' 

5 

4f 

if 

if 

6 

51 

if 

ill 

1A 

51 
6 

2i 

51 
51 

5 
6J 

u 

5 

if 

1M 

tapping  must  be  smaller  than  the  tap  by  nearly,  if  not  quite,  twice 
the  depth  of  the  thread.,  The  shape  of  the  thread  partly  determines 
the  amount  to  be  subtracted  from  a  tap  diameter.  There  are  now 
recognized  as  standard,  five  different  threads — sharp  or  V;  Franklin 
Institute  or  United  States  standard;  Whitworth;  International  or 
metric;  and  the  29  degrees  or  Acme.  These  shapes  will  be  described 
and  compared  under  "Screw  Cutting".  Table  II  shows  the  diam- 
eters of  the  holes  that  are  to  be  drilled  for  cutting  the  various  sizes 
of  the  threads  according  to  the  United  States  standard  and  the 
ordinary  V-thread. 

Hand  taps  are  most  commonly  used  in  shop  practice,  and  a 
description  of  their  operation  will  answer  for  all  styles.  They  are 
usually  sold  in  sets  of  three — taper,  plug,  and  bottoming — Fig.  81. 

Hand  Tapping.  The  cutting  of  a  thread  with  a  tap  is  not  a 
difficult  operation  but  requires  care  in  the  manipulation.  The  tap 
does  not  need  to  be  forced  into  the  work,  since  the  thread  will  draw 
it  forward.  The  tapering  of  the  tap  has  a  two-fold  effect.  No  one 
thread  does  all  of  the  work  in  the  removal  of  the  metal ;  each  succeed- 
ing thread  removes  a  small  amount  until  the  full  thread  has  entered 


MACHINE  SHOP  WORK  49 

the  hole.  The  second  effect  is  that,  as  in  the  case  of  a  reamer,  the 
tap  is  easily  entered  and  started.  Care  must  always  be  exercised 
at  this  point  of  the  work.  The  taper  of  the  tap  allows  it  to  easily 
enter  the  hole  and  also  makes  it  possible  for  it  to  enter  at  an  angle. 
If  it  is  started  in  the  latter  condition,  the  thread  will  not  be  at  right 
angles  to  the  hole.  The  degree  of  care  needed  in  the  starting  of 
the  tap  depend^  nipon  the  job  that  is  to  be  done.  In  the  case  of  tap- 
ping a  nut,  it  will  usually  be  quite  sufficient  to  set  the  tap  by  the 
eye.  In  finer  classes  of  work,  however,  the  tap  should  be  set  with  a 
square.  Start  the  tap  into  the  hole  and  place  a  square  on  the  sur- 
face beside  it  in  two  positions  at  right  angles  to  each  other  and  see 
that  the  tap  stands  parallel  to  the  vertical  blade. 

Starting  the  Tap.  When  holes  have  been  drilled  that  are  to  be 
tapped,  a  good  way  of  setting  the  tap  is  to  put  a  center  in  the  drill 
spindle.  Put  the  tap  into  the  hole  and  bring  this  center  down  into 
the  center  hole  in  the  head  of  the  tap;  this  will  steady  the  latter 
while  it  is  being  started. 

In  using  the  tap,  it  is  well  to  work  it  back  and  forth.  This 
allows  the  chips  to  work  clear  of  the  cutting  edges,  and  the  oil  to 
cover  them.  In  case  of  heavy  work,  it  is  possible  to  drive  the  tap 
with  the  drill  spindle,  but  when  thus  driving  a  tap  in  a  machine, 
the  backing  up  is  impossible. 

Use  of  Bottoming  Tap.  Sometimes  a  thread  is  to  be  cut  down 
to  the  bottom  of  a  hole  that  does  not  pass  entirely  through  the  metal. 
In  this  case  the  bottoming  tap  is  used.  This  is  a  tap  that-i&  not 
tapered  at  the  entering  end.  The  method  of  working  is  to  first  cut 
the  thread  as  far  as  possible  with  the  plug  tap  and  then  use  the 
bottoming  tap,  which  will  enter  easily  and  can  be  driven  to  the 
bottom. 

Machine  Tapping.  Machine  tapping  is  best  done  by  using  a 
frictional  tapholder,  that  is,  one  in  which  the  friction  is  enough  to 
cut  the  threads,  but  which  will  slip  when  the  tap  strikes  the  bottom 
of  the  hole.  This  will  insure  the  hole  being  tapped  to  the  bottom 
and  avoid  all  danger  of  breaking  the  tap.  To  withdraw  the  tap,  the 
machine  is  reversed,  usually  at  a  higher  speed  than  used  in  tapping. 

Lubrication.  WThen  tapping  wrought  iron  and  steel,  a  plentiful 
supply  of  lard  oil  should  be  used.  On  brass  the  use  of  oil  is  unneces- 
sary. 


50 


MACHINE  SHOP  WORK 


Threading  Dies 

Dies  are  used  for  cutting  threads  on  bolts  and  other  similar 
parts  to  be  placed  in  holes  w^hich  have  been  threaded  by  taps.  The 
general  rules  given  for  the  use  of  taps  apply  to  dies.  As  the  number 
of  threads  in  a  die  is  much  less  than  on  a  tap,  and  because  the 

chips  have  a  much  freer  exit,  it  is  not 
as  necessary  to  back  up  a  die  as  it  is 
a  tap. 

Solid  Dies.  Dies  for  small  work  are 
usually  made  solid,  as  shown  in  Fig.  82, 
and  often  have  a  slight  adjustment  for 
altering  the  size.  They  cannot  be  sharp- 
ened, but  have  an  advantage  in  readily 
centering  on  the  work.  As  the  full  thread 

rig.  82.   Threading  Die  is  cut  at  °ne  passage  of  the  die,  it  takes 

considerable  power  to  operate  solid  dies  of 

large  size.    For  this  reason,  hand-operated  solid  dies  are  seldom  used 
above  one-half  inch.    The  holder  or  die  stock  shown  in  Fig.  83  has 


Fig.  83.    Self-Centering  Die 

a  guide  to  hold  the  work  at  right  angles  to  the  die,  but  die  stocks 
are  often  made  without  this  convenience. 

Split  Dies.  The  split  form  of  die,  generally  known  as  the 
jamb-die,  Fig.  84,  can  be  easily  resharpened,  has  unlimited  adjust- 
ment for  size,  and  cuts  the  thread  by  easy  stages,  as  it  were.  It  is 


MACHINE  SHOP  WORK 


51 


made  in  sizes  up  to  2  inches  and  is  for  hand  operation  only.  The 
holder  for  this  form  of  die  is  called  a  screw  plate,  Fig.  85.  These 
are  not  furnished  with  guides  for  the  work. 

Cutting  Pipe  Threads.  Another  common  form  of  thread 
cutting  is  that  on  wrought-iron  pipe.  The  pipe  thread  is  rounded 
slightly  at  top  and  bottom  and  is 
made  tapering  at  the  rate  of 
three-quarters  of  an  inch  per 
foot.  The  dies  are  'usually  solid, 
square  in  form,  and  the  die  stocks 
are  provided  with  a  ring  which 
fits  over  the  pipe  and  serves  to 
hold  it  square  with  the  die.  This 
avoids  the  danger  of  cutting 
the  thread  at  an  angle  with  the  Fie- 84-  sPUt  Die 

pipe  axis. 

Cutting  Bolt  Threads.  Bolt  cutting  is  seldom  done  by  hand, 
such  work  being  usually  performed  on  bolt-cutters.  This  is  ordi- 
narily the  roughest  and  cheapest  class  of  work,  and  the  running  of 


Fig.  85.     Threading  Die  Holder 

the  bolt-cutter  is  often  the  first  work  to  which  the  apprentice  is 
assigned. 

An  ordinary  bolt-cutter  is  shown  in  Fig.  86;  its  operation 
is  as  follows:  The  dies  are  held  in  the  head  A.  Instead  of 
being  solid,  as  in  Fig.  82,  they  are  made  in  sections  and  can  be  opened 
or  closed  by  the  movement  of  the  lever  B.  A  chuck  C  is  placed  on 
a  traveling  head,  and  this  can  be  moved  back  and  forth  by  the  hand- 


52 


MACHINE  SHOP  WORK 


wheel  D.  The  method  of  working  is  very  simple.  The  dies  in  the 
head  are  closed  in  order  to  be  in  the  working  position.  The  bolt  to 
be  cut  is  gripped  in  the  chuck  by  turning  the  handle  E  and  forced 
against  the  dies  by  the^  handle  D.  As  soon  as  the  dies  have  taken 


Fig.  86.     Bolt  Cutter 

hold,  they  draw  the  bolt  ahead.  When  a  sufficient  length  of  thread 
has  been  cut,  the  dies  are  opened  and  the  bolt  withdrawn.  This 
avoids  the  necessity  of  backing  out,  as  would  be  required  if  the  dies 
were  solid.  While  the  thread  is  being  cut,  the  dies  are  kept  flooded 
with  oil. 


HISTORICAL  DEVELOPMENT  OF  HARTNESS  FLAT  TURRET  LATHE 

Courtesy  of  Jones  and  Lamson  Machine  Company,  Springfield,  Vermont 


I       MACHINE  SHOP  WORK 

PART  II 

POWER=DRIVEN  TOOLS 

LATHES 

Origin.    The  lathe  is  undoubtedly  the  oldest  form  of  machine 
tool.     Its  prototype  is  the  drilling  machine.     Each  of  these  machine 


Fig.  87.     Typical  Speed  Lathe  for  Hand  Turning 

tools  probably  developed  from  that  earliest  example  of  mechanical 
rotary  motion  of  which  we  have  a  record,  the  "potters'  wheel". 

Speed  Lathes.    This  term  includes  that  line  of  lathes  illus- 
trated in  Fig.  87,  which  shows  a  typical  design.    These  machines 


54 


MACHINE  SHOP  WORK 


are  sold  in  the  open  market  in  a  variety  of  sizes  from  the  smaller 
jewelers'  lathe  to  those  having  a  swing  of  12  inches.  All  types 
and  all  sizes  are  designed  to  be  used  with  hand-controlled  cutting 
tools,  and  are  often  designated  as  hand  lathes.  If  desired,  they  can 
be  driven  by  foot  power  and  are  then  often  termed  foot  lathes. 

Tools  for  Hand  Turning.    In  turning  brass  and  composition 
the  tools  cut  by  a  scraping  action,  and  are  almost  always  held  at 


Fig.  88A.     Planisher 


Fig.  88B.     Graver 


Fig.  88C.     Round  Nose 
Fig.  88.     Cutting  Tools  for  Hand  Turning 

or  below  the  center.  The  three  tools  shown  in  Fig.  88,  called  the 
planisher,  graver,  and  round  nose,  are  typical  of  all  the  tools  neces- 
sary for  turning  brass,  etc.  The  manner  of  holding  these  tools  in 
connection  with  the  T-rest  is  illustrated  by  the  planisher  in  Fig.  89. 
Fig.  90  shows  another  view  of  the  T-rest.  Typical  hand  tools  for 
cutting  iron  and  steel  are  the  diamond  point  or  graver  and  the 
round  nose,  shown  in  Fig.  91.  They  are  used  differently  from 


MACHINE  SHOP  WORK 


55 


hand  tools  for  brass,  in  that  the  cutting  edge  is  carried  above  the 

center,  and  the  metal  is  removed  by  cutting  instead  of  scraping. 

Graver.    The  graver  frequently  takes  the  place  of  the  planisher, 

for  it  can  be  used  as  shown  in  Fig.  92,  either  on  the  outside  or  on  the 


Fig.  89.     Hand  709!  Rest  with  Tool 
in  Position 


Fig.  90.     Simple  Hand 
Tool  Rest 


end  of  a  piece  of  work.  The  graver  can  be  used  on  brass  for  a  great 
variety  of  operations;  but  its  use,  except  in  the  hands  of  an  expert 
workman,  is  attended  by  the  danger  of  catching  in  the  soft  metal 
and  thus  breaking  the  tool  or  spoiling  the  work. 


Fig.  91.     Typical  Hand  Tools  for  Steel  Turning 


Round  Nose.  The  round  nose  is  used  solely  for  turning  concave 
surfaces,  being  held  as  high  on  the  work  as  proper  cutting  will  allow, 
as  shown  in  Fig.  93. 


56 


MACHINE  SHOP  WORK 


Slide  Rest.  To  make  the  hand  lathe  more  rapid  and  more 
certain  in  operation,  it  is  frequently  provided  with  a  tool  holder 
called  the  slide  rest,  as  shown  in  Fig.  94.  This  holds  the  tool  rigidly 
and  guides  it  mechanically,  so  that  the  work  is  done  more  rapidly 
than  with  the  hand  tools.  Slide  rest  tools  are  miniatures  of  those 


Fig.  92.     Position  of  Tool  for  Turning  Steel 

used  on  larger  lathes,  hence  a  description  will  not  be  given  at  this 
point. 

Engine  Lathes.  This  type  of  machine  tool  is  well  illustrated 
by  Fig.  95,  which  shows  the  common  cone  belt-driven  screw-cutting 
engine  lathe  of  ordinary  dimensions.  It  is  commonly  sold  in  sizes 
from  10-inch  swing  to  30-inch  swing.  Larger  sizes  are  usually  built 

to  order.  When  an  engine 
lathe  is  used  for  turning,  the 
tool  is  rigidly  held  in  a  "tool 
post"  clamped  to  the  cross- 
slide,  and  is  not  directly  hand 
controlled.  The  modern  en- 
gine lathe  is  designed  usu- 
ally so  that  by  combining  a 
direct  belt-driven  cone  and 
suitable  back  gears  a  range 
of  at  least  eight  rotative 
spindle  speeds  are  obtained. 

The  engine  lathe  illustrated  in  Fig.  95  has  a  strong  cast-iron 
bed  A  carried  on  four  well  braced  legs  that  may  be  bolted  to  the  floor, 
though  the  weight  of  the  machine  may  be  sufficient  to  hold  it  in 
position.  On  the  left-hand  end  of  the  bed  there  is  fastened  the 
headstock  B,  which  carries  the  main  running  gear  of  the  machine. 


Fig.  93.     Hand-Turning  a  Fillet 


MACHINE  SHOP  WORK        .  57 

At  each  end  of  the  headstock  there  is  a  bearing  for  the  spindle. 
Running  loosely  on  the  spindle  and  between  the  bearings  is  the  cone 
pulley  C  to  which  the  pinion  D  is  attached. 

Gear  Drive.  The  back  gearing  is  designed  to  reduce  the  speed 
of  the  spindle  without  changing  the  belt  speed.  The  mechanism  of 
the  back  gearing  is  clearly  shown  in  Fig.  96.  The  large  gear  E 
alone  shows  in  Fig.  95.  It  is  driven  by  the  pinion  D  which  is 
attached  to  the  cone.  Referring  interchangeably  to  Figs.  95  and  96, 
a  pinion  on  the  same  sleeve  as  the  gear  E  drives  the  gear  at  the 
right  of  the  cone  c,  which  gear  is  keyed  to  the  work  spindle.  When 


Fig.  94.     Hand  Lathe  Slide  Rest 


the  back  gearing  is  not  in  use,  it  is  thrown  out  of  mesh  with  the  gears 
on  the  pulley  and  spindle  by  means  of  a  shaft  having  eccentric 
bearings  upon  which  it  turns;  at  the  same  time  the  cone  pulley 
locks  fast  to  the  gear  at  its  right;  the  work  spindle  then  turns  with 
the  cone  pulley.  With  the  back  gearing  in  use  the  spindle  runs  more 
slowly,  with  the  belt  on  the  same  step  of  'the  cone,  than  it  does 
when  driven  direct. 

Work  Spindle  Arrangement.  The  work  spindle  projects  through 
the  bearings  at  each  end.  At  the  right  it  is  usually  threaded  to 
receive  a  faceplate  F,  and  is  also  bored  out  and  tapered  for 
a  work  center  G.  This  center  is  called  the  live  center  because 


58 


MACHINE  SHOP  WORK 


it  turns  with  the  spindle.     The  dead  center  H  is  in  the  tailstock, 
and  does  not  turn.     At  the  left  the  work  spindle  projects  beyond 


the  bearings  and  presses  axially  against  a  thrust  step.  The  cone 
pulley  I  serves  as  the  driving  pulley  for  a  narrow  belt  running  to 
the  corresponding  pulley  K  on  the  feed  rod  N.  The  pinion  J 


MACHINE  SHOP  WORK 


59 


drives  the  lead-screw  0  through  the  intermediate  gear  M  and  the 
direct  gear  L. 

Handling  the  Work.  The  work  is  held  on  the  centers  G  and  H, 
the  distance  between  which  is  adjusted  by  moving  the  tailstock  S 
(sometimes  called  the  tailblock).  The  latter  is  held  to  the  bed  by  a 
clamp  and  bolts  tightened  by  the  nuts  T.  To  move  the  tailstock, 
these  nuts  are  slackened  and  the  stock  moved  to  the  proper  position. 
The  final  adjustment  is 
made  by  turning  the 
hand  wheel  Q,  which 
rotates  a  screw  in  the 
sleeve  P.  Sleeve  P  works 
in  a  nut  in  the  spindle 
of  the  dead  center  II, 
which  is  thus  moved  in 
and  out.  When  the  cen- 
ters have  been  properly 
adjusted  and  the  work 
is  in  position,  the  dead 
center  is  clamped  by  the 
handle  R. 

When  work  is  to  be 
turned,  the  tool  is  prop- 
erly adjusted,  and  the 
carriage  U  moved  along 
the  bed.  This  move- 
ment is  accomplished  by 
means  of  gearing,  wrhich 
is  placed  behind  the 
apron  of  the  carriage, 
and  driven  by  the  shaft  N  by  the  cone  pulley  K,  which  is  keyed  to 
shaft  N.  The  driving  gearing  meshes  with  a  rack  beneath  the 
upper  ledge  of  the  bed.  Connection  between  the  gearing  and 
shaft  N  is  made  by  a  friction  clutch.  The  carriage  may  also  be 
moved  by  hand,  by  turning  the  hand  wheel  F,  to  which  is  keyed  a 
pinion  indirectly  meshing  into  the  rack. 

Tool-Feeding  Mechanism.    The  tool  is  fed  to  the  work  and  with- 
drawn from  it  by  turning  the  cross-feed  handle  W.     By  means  of 


Fig.  96.     Typical  Set-Up  of  Gears  on  Lathe 
Using  Back  Gear 


60  MACHINE  SHOP  WORK 

the  screw  and  nut,  this  moves  the  cross-slide  X.  These  arrange- 
ments permit  any  desired  transverse  or  longitudinal  position  of  the 
tool.  The  motion  of  the  carriage  is  usually  from  right  to  left  when  at 
work.  When  screws  are  to  be  cut,  a  different  feed  is  used.  In 
ordinary  turning,  there  will  be  a  variation  in  the  relations  between 
the  rotation  of  the  work  and  the  longitudinal  motion  of  the  tool, 
due  to  the  slipping  of  the  belt  connecting  the  cone  pulleys  /  and  K, 
or  to  the  slipping  of  the  friction  clutch  which  connects  the  shaft  N 
to  the  driving  gear.  To  cut  a  screw-thread,  it  is  necessary  that 
there  shall  be  no  relative  change  in  the  rotation  of  the  work  and 
the  longitudinal  motion  of  the  tool.  In  other  words,  the  tool  must 
travel  a  given  distance  for  every  revolution  of  the  work.  To  accom- 
plish this,  the  carriage  is  driven  by  the  lead-screw  0  working  in  a  nut 
set  in  the  carriage.  The  screw  is,  in  turn,  driven  by  the  train  of 
gears  J,  M ,  and  L.  The  gear  J  is  keyed  to  the  stud.  The  inter- 
mediate gear  M  runs  loose  on  a  sleeve.  The  gear  L  is  keyed  to  the 
lead-screw  0.  By  changing  the  sizes  of  the  gears  used  on  the  stud 
and  the  screw,  any  desired  thread  may  be  cut.  The  size  of  the 
intermediate  gear  M  has  no  effect  on  the  thread  being  cut.  This 
gear  M  is  used  to  connect  the  other  two  gears  L  and  J  and  can  be 
adjusted  to  any  desired  position  for  that  purpose. 

LATHE  EQUIPMENT 

Setting  Up  Change=Gears  for  Thread=Cutting.  The  descrip- 
tions in  the  preceding  pages  apply  particularly  to  the  usual  form  of 
engine  lathe,  and  a  clear  understanding  of  its  construction  and  the 
details  of  its  essential  parts  is  desirable.  Instead  of  being  placed 
directly  on  the  main  spindle,  the  first  gear  J  o£  the  train  of  "change- 
gears"  used  for  driving  the  lead-screw  0  for  thread-cutting,  is  fixed 
to  the  stud  shaft  H,  shown  at  B  in  the  diagram,  Fig.  97,  upon  the 
inner  end  of  which  is  fixed  the  stud  shaft  gear  G,  which  engages  a 
gear  F  of  the  same  diameter  fixed  to  the  main  spindle  at  the  left  of 
the  cone  pinion  D.  By  this  means  the  stud  shaft  H  rotates  at 
exactly  the  same  speed  as  the  main  spindle.  The  small  feed-cone 
I  is  fixed  to  the  stud  shaft  H,  and  the  large  feed-cone  K  to  the  feed- 
rod  N,  by  which  ordinary  turning  feeds  are  produced. 

Referring  to  the  end  elevation  A  in  Fig.  97,  the  change-gears  J 


MACHINE  SHOP  WORK 


61 


and  L  being  of  equal  diameters  and  equal  numbers  of  teeth,  it 
follows  that  the  lead-screw  0  will  revolve  at  the  same  rate  as  the  main 
spindle.  Therefore,  if  the  lead-screw  is  cut  with  four  threads  per 
inch,  the  lathe  carriage  will  move  a  quarter  of  an  inch  at  each  revolu- 
tion, and  the  lathe  will  cut  four  threads  per  inch. 

The  intermediate  gear  M  does  not  change  the  rate  of  speed, 
although  it  reverses  the  direction  of  revolution. 

If  the  change-gear  J  is  only  one-half  the  diameter  of  the  change- 
gear  L,  the  lead-screw  0  will  revolve  only  one-half  as  fast  as  the  main 
spindle,  and  therefore  the  lathe  will  cut  eight  threads  per  inch;  but 
if  the  case  is  reversed  and  the  change-gear  L  is  only  half  the  diam- 


Fig.  97.    End  and  Front  Elevation  of  Engine  Lathe  for  Thread  Cutting 

eter  of  the  change-gear  J,  the  carriage  will  move  twice  as  fast  as  in 
the  first  instance,  and  the  lathe  will  cut  two  threads  per  inch.  From 
this  condition  we  deduce  the  rule: 

The  thread  to  bt  cut  will  bear  the  same  ratio  to  that  of  the  lead- 
screw,  as  the  two  change-gears  bear  to  each  other. 

The  ratio  will  be  the  same  whichever  change-gear  is  the  larger. 
It  must  be  remembered,  however,  that  if  the  change-gear  on  the 
stud  shaft  is  the  larger,  the  resultant  thread  will  be  coarser  than  the 
lead-screw,  and  vice  versa. 

To  cut  any  desired  number  of  threads  per  inch,  we  first  find  the 
ratio  which  the  desired  number  of  threads  bears  to  the  number  of 
threads  on  the  lead-screw,  and  then  select  such  change-gears  as 
bear  this  ratio  to  each  other. 


62 


MACHINE  SHOP  WORK 


The  gears  will  revolve  in  the  directions  shown  by  the  arrows; 
therefore  the  lead-screw  revolves  in  the  direction  opposite  to  the  main 
spindle,  so  that  with  a  right-hand  thread  on  the  lead-screw  0  (the 
usual  arrangement),  the  lathe,  geared  as  here  shown,  will  cut  left- 
hand  threads.  If  right-hand  threads  are  desired,  the  intermediate 
gear  M  is  moved  to  the  left,  and  another  gear  introduced  between  it 
and  the  gear  L.  The  usual  type  of  engine  lathe  is  therefore  provided 
with  an  auxiliary  set  of  gearing  for  the  purpose  of  reversing  the 
rotation  of  the  stud  shaft  PI.  These  auxiliary  gears  are  known  as 

tumbler  gears. 

Compounding.  When  the 
proper  ratio  cannot  be  obtained 
by  the  use  of  the  change-gears 
at  hand,  or  when  the  gears  of 
the  desired  numbers  of  teeth 
would  be  too  small  to  connect 
properly,  or  too  large  to  put  in 
place,  the  method  called  com- 
pounding is  used.  Assume  that 
the  ratio  of  4  to  1  is  required 
Referring  to  Fig.  98,  a  36- 
toothed  gear  J  is  placed  on  the 
stud  shaft,  and  a  72-toothed 
gear  L  on  the  lead-screw.  On  the  sleeve  stud  are  two  gears,  a  48- 
and  a  24-toothed,  fixed  to  each  other  by  placing  them  on  a  splined 
compounding  sleeve  which  runs  loosely  on  the  stud.  The  36-gear  is 
engaged  with  the  48-,  and  the  24-  with  the  72-toothed  gear,  as 
shown.  Front  and  edge  views  of  these  gears  are  given  to  show 
clearly  their  relative  positions. 

The  results  of  this  combination  are:  If  the  36-gear  en- 
gaged the  72-gear,  the  ratio  would  be  2;  and  if  the  24-gear 
engaged  the  48-gear,  the  ratio  would  also  be  2.  These  ratios 
multiplied  would  be  4,  as  required.  As  shown,  the  ratios  are: 
36  to  48,  ratio  1J;  and  24  to  72.  ratio  3 — which  ratios  multiplied 
together  produce  4. 

The  effect,  then,  of  introducing  the  24-  and  48-gears  instead  of 
a  single  intermediate  (usually  called  an  idler  gear,  as  it  does  not  affect 
ratios),  is  to  double  the  ratio  existing  between  the  gear  on  the  stud 


Fig.  98.     Compounding  Gears 


MACHINE  SHOP  WORK 


63 


shaft  and  the  gear  on  the  lead-screw.  The  combination  just 
described  will  cut  a  16-pitch  thread  on  a  lathe  having  a  4-pitch 
lead-screw.  (Usually  a  lathe  will  cut  this  thread  without  com- 
pounding. The  gears  shown  and  described  are  given  merely  as  a 
simple  example.) 

Should  the  above  order  of  arranging  the  gears  be  reversed,  the 
effect  will  be  to  divide  the  thread  ratio  instead  of  multiplying  it;  and 
instead  of  cutting  16  threads  per  inch,  the  lead-screw  threads  of  4 
to  an  inch  will  be  divided  by  4,  producing  1,  and  the  lathe  will  cut 
1  thread  per  inch. 

Lathes  are  usually  provided  with  compounding  gears  of  the 
ratios  of  2  to  1 — as  24  to  48,  36  to  72,  and  so  on.  But  it  is  very 
convenient  to  have  those  of  3  to  1— as  24  to  72,  36  to  108,  etc. 


Fig.  99.     End  and  Front  Elevation  of  Rapid  Change-Gear  Device 

It  is  always  advisable  to  use  as  large  change-gears  as  possible, 
as  the  revolutions  of  the  lead-screw  will  be  more  regular  and  steady, 
the  strain  on  the  gear  teeth  will  be  less,  and  smoother  and  more 
accurate  work  will  result. 

Rapid  Change-Gear  Devices.  The  more  recent  development 
of  the  thread-cutting  mechanism  of  engine  lathes  aims  to  arrange 
the  change-gears  so  that  any  desired  thread  may  be  cut  without 
removing  or  replacing  any  of  the  gears.  To  accomplish  this,  all 
the  necessary  change-gears  are  permanently  located  on  the  lathe, 
and  any  one  of  them  may  be  brought  into  use  as  required,  by  shifting 
one  or  more  levers  or  equivalent  devices. 

One  of  the  most  prominent  of  these  devices  is  shown  in  Fig.  99, 
which  illustrates  at  the  left,  an  end  and,  at  the  right,  a  front 
elevation  of  the  device  applied  to  an  engine  lathe.  Motion  is  com- 


64 


MACHINE  SHOP  WORK 


municated  from  the  work  spindle  by  means  of  the  gear  A  on  the 
head  shaft,  and  through  the  gears  B  and  C,  to  the  supplemental 
shaft  77,  upon  which  is  fitted  a  forked  sliding  arm  G.  This  sliding 
arm  G  carries  a  pinion  D  splined  to  the  shaft  77,  and  also  a  con- 
necting pinion  E  journaled  in  it  and  capable  of  engaging  either 
one  of  the  sets  of  change-gears  F,  which  are  fixed  upon  the  lead-screw 
J,  by  sliding  the  lever  to  the  right  or  left,  raising  it  until  the  gears 
engage  properly,  and  permitting  the  pin  on  the  thumb-lever  K 
to  enter  one  of  the  series  of  holes  shown  in  the  gear  casing  and  thus 
secure  the  lever  G  and  connecting  pinion  E  in  proper  position  to 
transmit  motion  for  the  supplementary  shaft  H  to  the  lead-screw  J. 

An  index  on  the  outside  of 
the  gear  casing  gives  the 
necessary  information  as  to 
the  position  of  the  lever  G 
for  any  desired  thread.  No 
calculations  are  necessary. 
Size  of  Lathe.  In  this 
country,  the  size  of  a  lathe 
is  designated  by  the  great- 
est diameter  it  will  swing 
over  the  guides,  and  by  the 
length  of  the  bed.  The  one 
illustrated  is  known  as  a 
14-inch  by  8-foot  lathe.  In 
England,  the  distance  from 

the  guides  to  the  center  is  the  unit  of  size,  and,  in  a  few  cases, 
the  greatest  distance  between  centers  is  considered  to  be  the  length 
of  the  lathe.  Thus  a  15-inch  lathe  in  England  would  be  a  30-inch 
lathe  in  the  United  States. 

Attachments.  The  attachments  usually  furnished  without  extra 
charge  are  a  large  faceplate  of  the  full  swing  of  the  lathe,  a  center 
rest,  and  a  follower  rest.  The  small  faceplate  is  used  only  for  driv- 
ing the  work  indirectly  through  suitable  attachments. 

Faceplate.  The  large '  faceplate  shown  in  Figs.  95  and  100 
is  often  used  as  a  direct  support  for  the  work,  the  T-slots  and  other 
openings  being  used  for  bolting  and  clamping  the  work  firmly  to  the 
faceplate. 


Fig.  100.     Heavy  Faceplate 


MACHINE  SHOP  WORK 


65 


Center  Rest.  When  work  is  being  done  on  the  end  of  a  shaft 
so  that  the  tailstock  cannot  be  used,  it  is  necessary  to  support  the 
shaft  in  some  other  way.  This  is  done  by  means  of  the  center  rest, 
shown  in  Fig.  101.  This  consists  of  a  frame  hinged  at  A,  and  fitted 
with  three  movable  jaws  EBB.  The  rest  is  clamped  to  the  lathe- 
bed  in  the  proper  place.  The  jaws  BJZB  are  then  adjusted  to  form 


Fig.  101.    Typical  Center  Rest 

a  bearing  for  the  work,  care  being  taken  that  the  axis  of  the  work 
coincides  with  the  axis  of  the  lathe.  Unless  it  coincides,  the  work 
will  not  be  turned  true;  that  is,  the  end  will  not  be  square,  but  will  be 
hollowed  or  conical,  as  shown  somewhat  exaggerated  in  Fig.  102. 
The  center  rest  is  also  used  to  support  or  steady  long  shafts  that  are 
being  turned. 


66  MACHINE  SHOP  WORK 

After  adjusting  the  center  rest  to  size,  it  can  be  moved  along 
the  bed  of  the  lathe  without  changing  its  relation  to  the  lathe  axis; 


Fig.  102.     Diagrams  Showing.  Effects  When  Work  is  Not  Held  True  in  Cutting 


Fig.  103.     Combination  Chuck 


but  care  must  be  taken  not  to  reverse  the  center  rest  in  the  lathe, 
as,  in  most  cases,  such  action  would  necessitate  a  readjustment. 


MACHINE  SHOP  WORK 


67 


The  names  back  rest  and  steady  rest  are  synonymous  with  center 
rest,  the  use  of  the  device  often  determining  the  name. 

Follower  Rest.  The  follower  rest  serves  some  of  the  purposes 
of  the  center  rest,  but  is  fastened  to  the  carriage,  and  moves  with 
it  at  the  point  of  greatest  stress.  It  may  consist  of  adjustable  jaws 
or  a  solid  ring  to  slip  over  the  piece  being  turned.  It  is  especially 
valuable  in  turning  shafting  and  other  work  where  the  ratio  of  length 
to  diameter  is  very  great. 

Chucks.  The  lathe  chuck,  Fig.  103,  consists  of  a  body  which 
is  fastened  to  a  special  faceplate  in  such  a  way  that  it  is  concentric 
with  the  spindle.  The  three  jaws  ^4^4  can  be  moved  in  and  out 
toward  or  from  the  center,  by  turning  the  screw-heads  B.  These 
chucks  are  used  either 
universal  or  independ- 
ent. If  used  universal, 
all  the  jaws  are  oper- 
a  t  e  d  simultaneously. 
That  is,  when  one  of 
the  screw-heads  B  is 
turned,  all  of  the  jaws 
are  moved  an  equal 
distance  toward  or  away 
from  the  center.  This 
makes  it  possible  to  put 
the  work  in  position  quickly  if  it  is  approximately  round  in  its 
unfinished  condition.  With  the  independent  chuck,  Fig.  104, 
each  jaw  is  operated  separately.  Such  a  chuck  is  used  for  holding 
pieces  of  irregular  shape  and  those  which  must  be  held  eccentrically. 
In  Fig.  103  the  universal  and  independent  features  are  combined 
in  one  tool,  means  being  provided  for  working  the  jaws  separately 
or  together  as  desired. 

In  using  a  universal  chuck,  each  screw  should  be  tightened. 
The  method  of  procedure  is  to  place  the  work  in  the  chuck,  and  turn 
one  screw-head  until  all  of  the  jaws  are  in  contact  with  the  piece  to 
be  worked  on.  Then  turn  the  chuck,  and  tighten  each  screw-head 
successively  until  each  one  is  tight  enough.  Owing  to  wear  and 
lost  motion,  it  is  sometimes  necessary  to  apply  the  wrench  to  each  one 
three  or  four  times  before  the  final  adjustment  is  effected. 


Fig.  104.     Lathe  Work  Chuck 


68 


MACHINE  SHOP  WORK 


Fig.  105.     Faceplate  Chuck  Jaw 


Universal  chucks  generally  have  three  jaws,  while  independent 
chucks  have  four.  It  follows  that  a  combination  chuck  is  not 
wholly  satisfactory,  because,  with  three  independent  jaws,  it  is 

very  difficult  to  adjust  work 
accurately,  and  with  four 
universal  jaws  it  is  equally 
difficult  to  get  every  jaw  to 
bear  on  the  work.  For  cer- 
tain classes  of  work — espe- 
cially valves  and  pipe  fit- 
tings— chucks  with  two  jaws 
are  often  used. 

The  large  faceplate  of  a 
lathe  can  be  made  into  an 
independent  chuck  by  attach- 
ing what  are  known  as  faceplate  jaws,  Fig.  105.  In  this  case, 
there  may  be  six,  eight,  or  more  jaws. 

As  work  chucks  are  expensive,  it  sometimes  happens  that  a 
piece  is  to  be  held  for  which  no  provision  is  made.  A  chuck  can  then 
be  made  of  wood,  as  shown  in  Fig.  106.  Two  pieces  of  wood  A  and 
B  are  bolted  together  by  the  bolts  EE,  while  separated  by  the 

filling  pieces  CC.  The  piece  is 
firmly  bolted  to  the  faceplate 
by  the  bolts  DD.  The  lathe  is 
then  run  at  high  speed,  and  the 
interior  bored  out  exactly  the 
size  of  the  piece  that  is  to  be 
held.  The  nuts  of  the  bolts 
EE  are  slackened,  and  the 
filling  pieces  CC  removed.  The 
piece  to  be  worked  on  is  then 
inserted,  and  by  tightening  the 
nuts  EEj  it  is  securely  clamped 
between  the  pieces  A  and  B. 
Lathe  Dogs.  As  the  fric- 
tional  contact  of  the  work  on  the  live  center  is  not  sufficient  to 
drive  it,  some  device  must  be  used  to  make  the  work  rotate  with  the 
center.  To  accomplish  thk,  a  lathe  dog  is  used.  For  round  work, 


Fig.  106.     Emergency  Chuck 


MACHINE  SHOP  WORK 


69 


Fig.  107.     Lathe  Dog  for 
Round  Work 


such  as  shafting,  a  dog  like  that  shown  in  Fig.  107  is  often  used. 
The  shaft  or  piece  to  be  turned  is  placed  in  the  hole  A,  and  held 
firmly  in  place  by  the  set  screw  B.  The  tail-piece  C  is  put  through 
a  hole  in  the  faceplate,  and  the  work  rotates 
with  the  live  center. 

While  this  type  of  dog  is  satisfactory  in 
most  cases,  the  contact  between  the  dog  and 
the  faceplate  being  beyond  the  end  of  the 
piece,  introduces  a  bending  strain  which  is 
appreciable  in  slender  work.  To  avoid  this, 
dogs  are  made  with  a  straight  tail,  and  driven 
by  a  stud  projecting  from  the  faceplate. 

For  work  other  than  round,  a  dog  such  as 
that  shown  in  Fig.  108  may  be  used.  The 
piece  to  be  worked  on  is  placed  between  the 
jaws,  and  held  in  position  by  the  bolts. 
The  holes  in  the  upper  jaw  are  made  larger 
than  the  screws,  in  order  that  the  angle 
between  the  jaws  may  be  varied.  The  con- 
nection between  the  faceplate  and  dog  is  made  as  with  Fig.  107. 

Mandrels.  Another  method  of  holding  work  is  by  the  use  of  a 
mandrel.  This  is  a  piece  of  steel  with  a  slight  taper;  the  ends  are 
flattened  for  the  lathe  dog,  as 
shown  in  Fig.  109.  It  frequently 
happens  that  a  piece  with  a  hole 
in  it  is  to  be  turned  or  finished 
over  its  outer  surface.  In  this 
case  a  dog  cannot  be  used,  and 
it  is  troublesome  to  hold  it  in  a 
chuck.  Such  a  piece  is  shown 
in  Fig.  110.  This  is  a  stuffing- 
box  gland.  If  it  were  to  be 
held  by  the  jaws  of  a  chuck, 
the  face  could  not  be  reached 

at  all,  and  only  a  portion  of  the  edge  J5,  whereas  a  dog  clamped 
to  it  would  offer  even  greater  obstruction.  The  method  of  using 
the  mandrel  is  to  ream  the  gland  out,  so  that  it  can  be  driven 
upon  the  mandrel.  When  this  is  done,  the  frictional  resistance 


Fig.  108.     Clamp  Dog 


70 


MACHINE  SHOP  WORK 


between  the  two  will  be  sufficient  to  drive  the  piece.     So  held  in 
place,  it  can  be  finished  over  its  outer  surface  with  but  one  setting 


Fig.  109.     Work  Mandrel 


Fig.  110.     Stuffing-Box  Gland  Held  on  Mandrel 

in  the  lathe.     All  finishing  possible  may  be  done  while  it  is  in 
the  chuck,  leaving,  in  this  case,  only  the  face  A  and  edge  B  to  be 

finished    while    on    the 
mandrel. 

Should  the  gland  be 
shaped,  as  shown  in^Fig. 
Ill,  it  would  be  neces- 
sary to  make  a  special 
mandrel  to  fit  the  bore. 
The  cylindrical  part  A 
of  the  mandrel  should  be 
a  driving  fit,  and  the 
part  B  a  loose  fit. 

Expanding  Man- 
drels.    Where  a  mandrel 
-  like  that  shown  in  Fig. 
109  is  frequently   used, 

Fig.  111.     Stuffing-Box  Gland  Requiring  Special  Mandrel        ,1  ,    .     .  ,, 

the  constant  driving  of 

the  work  on  and  off  will  wear  the  mandrel  to  a  smaller  diameter, 
causing  it  to  become  useless.     Again,  solid  mandrels  are  usually 


n. 


MACHINE  SHOP  WORK 


71 


made  of  standard  diameters,  varying  by  sixteenths  of  an  inch.  It 
sometimes  happens  that  a  piece  to  be  turned  has  a  hole  which  will 
not  fit  any  standard  solid  mandrel. 

To  overcome  these  difficulties,  an  expanding  mandrel  shown 
in  Fig.  112  is  much  used.    This  is  really  a  chuck,  so  arranged  that 


'  Fig.  112.     Diagram  Showing  Use  of  Expanding  Mandrel 

the  grips  can  be  forced  out  against  the  interior  of  the  hole.  When 
the  work  has  been  finished,  the  grips  are  again  drawn  in  and  the  piece 
removed.  Another  form  of  expanding  mandrel  is  shown  in  Fig.  113. 


Fig.  113.     Another  Form  of  Expanding  Mandrel 

Cutting  Tools.  General  Characteristics.  The  cutting  tools  used 
in  lathes  are  of  a  great  variety  of  shapes.  These  shapes  are  adapted 
to  the  work  that  is  to  be  done,  and  to  the  kind  of  finish  that  is  to 
be  left  upon  the  metal.  There  are  two  fundamental  requirements 
for  all  cutting  tools:  the 
cutting  edge  alone  must 
touch  the  metal;  the  edge 
must  be  keen.  A  typical 
form  of  tool  is  shown  in 
Fig.  114.  The  cutting  edge 
of  the  tool  at  A  is  in  con- 
tact writh  the  work.  The 
bottom  line  A  B  runs  back 
from  the  metal  and  does  not  touch  it.  The  top  face  AC  slopes  down 
and  back.  The  line  AD  is  a  tangent  at  the  cutting  point,  and  the 
line  AE  is  radial  at  the  same  point.  Therefore,  the  angle  DAE 


&  \IO\D 
Fig.  114.     Cutting  Tool  Angles 


72  MACHINE  SHOP  WORK 

is  always  a  right  angle.  The  angle  DAB  is  called  the  angle  of 
clearance,  and  should  be  small — in  lathe  tools,  not  over  10  degrees. 
The  angle  CA  E  is  called  the  angle  of  rake,  and  should  be  as 
great  as  circumstances  will  permit — about  20  degrees  on  lathe  tools 
for  wrought  iron  and  steel,  leaving  60  degrees  for  the  solid  or 
cutting  angle,  which  is  the  same  angle  as  that  used  in  the  case  of 
the  ordinary  cold  chisel. 

Material.  The  physical  qualities  of  the  material  to  be  turned 
will  to  a  great  extent  determine  the  cutting  angles  of  the  tool — first, 
as  to  whether  it  is  hard  or  soft;  and  second,  whether  it  is  crystalline 
or  fibrous.  The  degree  of  hardness  of  a  material  determines  how 
much  can  be  removed  in  a  given  time,  or — what  amounts  to  the 
same  thing — whether  the  speed  of  the  cutting  shall  be  fast  or  slow, 
and  whether  the  feed  shall  be  coarse  or  fine.  A  crystalline  or  fibrous 
nature  will  make  considerable  difference  in  the  top  angles  of  the  tools, 
and  this  will  be  readily  seen  in  the  tendency  of  a  crystalline  metal 
(as  cast  iron)  to  break  up  into  small  chips,  while  the  fibrous  turnings 
(as  wrought  iron)  will  curl  off  into  spiral  or  helical  shavings.  There- 
fore the  fibrous  material  will  require  tools  of  sharper  angles  than 
those  for  a  crystalline  metal. 

For  cutting  soft  brass  and  other  similar  metals,  the  top  surface 
AC  of  the  tool  will  be  practically  level,  while  the  face  angle  BAD 
will  be  3  degrees  or  frequently  less. 

Clearance.  Clearance  prevents  the  tool  from  rubbing  on  the 
work,  while  rake  adds  to  the  keenness  of  the  cutting  edge,  and  gives 
freedom  to  the  removal  of  the  chips.  A  tool  should  have  sufficient 
strength  at  the  cutting  point  to  do  the  work  required. 

Setting  the  Tool.  The  tool  should  be  set  so  that  the  cutting  edge 
will  coincide  very  nearly  with  a  horizontal  line  passing  through 
the  axis  of  the  work.  Most  machinists  set  the  cutting  edge  a  little 
above  this  horizontal  line.  When  so  set,  the  stress  tends  to  force 
the  tool  down  along  the  line  of  its  greatest  strength.  The  tool 
may,  however,  be  set  too  high.  If  this  is  done,  as  in  Fig.  115,  the 
angle  of  clearance  will  disappear,  and  the  curve  of  the  work  will 
rub  against  the  bottom  of  the  tool.  This  will  tend  to  force  the  tool 
out;  heating  the  tool  and  producing  a  rough  surface  on  the  metal 
being  turned.  If,  on  the  other  hand,  the  tool  is  set  too  low,  as  in 
Fig.  116,  the  cutting  edge  does  not  stand  in  line  with  the  motion 


MACHINE  SHOP  WORK 


73 


of  the  work  at  the  point  of  contact.  The  result  will  be  that  the 
metal  will  be  scraped  rather  than  cut,  as  there  is  no  rake;  and  the 
pressure  upon  the  tool  will  be  in  the  line  of  its  least  resistance,  as 
indicated  by  the  arrow.  Such  a  position  might  cause  the  point 
of  the  tool  to  break  off.  It  will  also  cause  the  tool  to  tremble  or 


Fig.  115.     Tool  Set  too  High 


Fig.  116.     Tool  Set  too  Low 


chatter  as  it  removes  the  chips,  leaving  a  rough  and  wavy  surface 
on  the  metal. 

As  stated  above,  most  machinists  prefer  to  set  the  cutting  edge 
a  little  above  the  center.  The  amount  the  tool  is  set  above  the 
center  is  slight,  and  of  course  depends  upon  the  character  of  the 
work,  and  upon  the  shape  of  the  cutting  tool.  The  angle  ACB, 
Fig.  117,  should  be  only  about  5  or  6  degrees. 

Tool=Posts.  The  tool  is  usually  held  to  the  carriage  by  means 
of  a  tool-post,  shown  in  Fig.  118.  The  post  consists  of  a  piece 
with  a  slotted  hole  through  the  center  for  the  tool  B.  A  ring  C 
slips  over  the  post  and  rests  upon  the  body  of  the  carriage.  This 
ring  may  be  beveled  as  shown,  to  provide  vertical  adjustment  for 
the  point  of  the  tool.  ^The 
post  has  a  collar  D  at  its 
lower  end,  that  goes  loosely 
into  a  slot  in  the  carriage. 
At  the  top  there  is  a  set 
screw  E.  When  the  tool 
has  been  properly  adjusted 
by  turning  the  ring  C  to  give 
it  the  correct  elevation,  the  set  screw  is  tightened  down  upon  the  top 
of  the  tool.  This  raises  the  tool-post  to  a  bearing  on  the  under  side 
of  the  slot,  and  clamps  the  whole  firmly  in  position. 

In  setting  the  tool,  it  should  be  done  with  the  cutting 
edge  as  far  back  toward  the  supporting  ring  as  possible.  If  it 


Fig.  117.     Standard  Setting  with  Cutting  Edge  of 
Tool  a  Little  Above  Center 


74 


MACHINE  SHOP  WORK 


has  too  much  overhang,  as  shown  by  the  dotted  lines  of 
Fig.  118,  it  will  spring  under  the  pressure  of  the  work  and  will 
tend  to  chatter. 

While  this  form  of  tool-post  is  used  more  than  any  other,  there 
are  certain  objections  to  it.     In  the  first  place,  changing  the  height 


Fig.  118.     Tool-Post  Holding  Tool  to  Carriage 

of  the  tool-point  also  changes  the  angles  of  rake  and  clearance. 
These  are  supposed  to  be  correct  when  the  base  of  the  tool  is  hori- 
zontal. Any  change  from  this  position  will  alter  these  angles 
materially.  Again,  this  post  is  not  rigid  enough  for  heavy  work. 
On  lathes  of  over  30-inch  swing,  the  style  of  tool-holder  shown  in 

Fig.  119  is  often  employed. 
English  manufacturers  use  it 
almost  exclusively  on  all 
sizes.  There  is  no  provision 
for  raising  and  lowering  the 
point  of  the  tool;  and  while 
this  is  not  of  serious  impor- 
tance on  large  lathes  (30-inch 
and  over),  it  becomes  a  mat- 
ter of  moment  when  turning 
the  kind  of  work  which  as  is  usually  handled  in  lathes  of  14-inch 
and  16-inch  swing. 

The  type  of  tool-post  shown  in  Fig.  120  has  two  beveled  rings 
to  adjust  the  height  of  the  tool. 


Fig.  119.     Tool  Holder  for  Heavy  Turning 


MACHINE  SHOP  WORK 


75 


The  Lipe  tool-post  shown  in  Fig.  121,  combines  the  good  points 
of  all  the  other  types;  the  tool  can  be  held  by  one  or  two  screws 
as  the  character  of  the  work  may  require,  and  the  tool  may  be 
adjusted  vertically  and  hor- 
izontally after  being  clamped 
down.   The  construction  and 
operation   of   this   tool-post 
are  so  evident  from  the  illus- 
tration, that  further  descrip- 
tion will  not  be  given. 

An  entirely  different 
method  of  adjusting  the  tool 
point  is  by  means  of  what  is 
called  the  elevating  or  rise- 
and-fall  rest,  shown  in  Fig. 
122.  In  this  type,  there  is 
a  T-shaped  casting  carried  on 
the  upper  part  of  the  carriage, 
supported  by  trunnion  screws 
at  the  front,  and  by  an  adjust-  Fig.  120.  Bevel  Ring  Tool-Post 


Fig.  121.     Lipe  Tool-Post 


76 


MACHINE  SHOP  WORK 


ing  screw  at  the  rear.  With  this  is  used  a  tool-post  as  shown  in 
Fig.  118,  with  a  plain  ring.  The  elevating  rest  is  used  quite 
extensively  on  small  lathes,  but  the  convenience  of  adjustment 
is  gained  by  a  loss  in  rigidity.  The  cross-rail  is  slender;  and  the 


Fig.  122.    Tool-Post  with  Rise-and-Fall  Rest 

elevating  portion,  being  supported  at  three  widely  separated 
points,  lacks  stiffness.  As  the  effective  swing  over  the  carriage 
is  limited  by  the  height  of  the  cross-rail  and  by  the  parts 
carried  above  it,  they  are  made  slender — in  fact,  too  slender  in 
many  cases. 

Turning  Tools.  Side  or  Facing  Tool.  A  very  common  form 
of  lathe  tool  is  shown  in  Fig.  123.  It  is  used  for  squaring  up  the 
ends  of  shafts,  facing  shoulders,  and  similar  work.  While  the 
ordinary  forms  will  not  remove  a  large  amount  of  metal,  they  can, 
when  made  thick  and  heavy,  be  used  for  making  roughing  cuts 
on  the  surface  of  cylindrical  wrork.  The  common  form  is  made 


Fig.  123.     Side  or  Facing  Tool 


Fig.  124.     Diamond  Point 


slender  in  order  to  work  between  the  dead  center  and  the  piece  in 
squaring  up  ends. 

Diamond  Point.     A  common  form  of  tool  for  turning  wrought 


MACHINE  SHOP  WORK 


77 


iron  and  steel  is  the  diamond  point,  shown  in  Fig.  124.  The  name 
is  derived  from  the  shape  of  the  top  face.  This  tool  has  both  front 
and  side  rake,  which  form  a  keen  edge  without  reducing  the  strength. 
It  is  used  for  finishing  only  when  the  point  is  ground  slightly  round- 
ing. In  finishing,  but  little  metal  should  be  removed  and  a  fine  feed 
used. 

The  feed  of  a  tool  is  the  amount  of  longitudinal  advance  at 
each  revolution  of  the  work. 

For  roughing  out  cast  iron,  a  strong  and  rapid  working  tool 
is  a  round  nose  with  considerable  side  rake.  For  finishing  wrought 


Fig.  125.     Tool  for  Finishing -Wrought 
Iron  and  Steel 


Fig.  126.     Tool  for  Finishing  Cast  Iron 


iron  and  steel,  a  modification  of  the  diamond  point,  as  shown  in 
Fig.  125,  is  often  used.  For  cast  iron,  a  square-nosed  tool,  Fig.  126, 
may  be  used.  The  square-nosed  tool  must  be  carefully  ground 
and  accurately  set;  otherwise  it  is  very  likely  to  gouge  into  the 
softer  parts  of  the  metal.  When  finishing  wrought  iron  and  steel, 
the  tool  should  be  liberally  supplied  with  oil  or  soda  water.  Cast 
iron,  on  the  other  hand,  is  usually  worked  dry,  both  in  roughing  out 
and  in  finishing. 

Cutting-0/  or  Parting  Tool.  This  tool  is  illustrated  in  Fig.  127. 
The  blade  is  quite  narrow — as  narrow,  in  fact,  as  the  character  of 
the  work  will  allow.  As  the  blade  needs  to  be  narrower  at  the  shank 
and  at  the  bottom  than  it  is  at  the  cutting  edge,  it  follows  that  the 
tool  will  be  weak.  It  must  be  set 
horizontally,  so  that,  as  the  tool  is 
fed  to  the  work,  only  the  cutting 
edge  will  touch  the  metal.  It  must 
also  be  set  so  that  the  cutting  edge 
will  pass  through  the  axis  of  the 

work  as  it  is  fed  to  the  center.  If  set  too  high,  it  will  cease  to 
cut  before  the  center  of  the  work  is  reached;  while  if  too  low, 
the  tool  has  a  poor  scraping  action,  and  will  leave  a  portion  of  the 
work  uncut.  On  work  held  between  centers,  one  should  not  attempt 


Fig.  127.     Cutting-Off  or  Parting  Tool 


78  MACHINE  SHOP  WORK 

to  cut  to  the  center  of  the  piece,  as  the  work  will  surely  ride  up 
onto  the  tool. 

Boring  Tools.    The  term  boring  as  used  in  machine  practice 
usually  means  methods  of  machining  internal  surfaces,  other  than 
~  those  of  common  drilling  and 

reaming.      Also    methods    for 
holding    the  work  other  than 


those  common  to  ordinary  drill- 
Fig.  128.     General  Form  of  Boring  Tool 

ing    and    chucking    operations 

are  often  used.  When  boring  machine  parts,  use  may  be  made 
of  the  common  inside  turning  tools  or  of  special  appliances  termed 
boring  bars. 

When  a  hole  is  to  be  bored  in  lathe  work,  tools  of  a  shape  different 
from  those  used  in  turning  should  be  used.     The  general  form  of  the 

tool  is  shown  in  Fig.  128.  The  length 
of  the  shank  depends  on  the  depth  of 
the  hole  to  be  bored,  for  it  must  be 
long  enough  to  reach  from  the  tool-post 
to  the  bottom  of  the  hole.  This  over- 
hang makes  the  tool  more  likely  to 
spring,  and  necessitates  a  much  lighter 
cut  being  taken  than  when  removing 
the  same  amount  of  metal  by  outside 
turning  tools.  The  result  of  this  lighter 

Fig.  129.     Boring  Tool  Set  for  & 

cut   is    seen   in   the   increase   of   time 

required  to  remove  a  given  amount  of  stock.  The  shape  of  the 
cutting  edge  is  practically  the  same  as  that  of  the  tools  for  turn- 
ing, except  that  the  boring  tool  must  have  more  clearance  to 
avoid  striking  the  work.  Therefore,  with  the  same  solid  angle, 

the  tool  will  have  less  rake.  The 
reason  for  this  will  be  seen  by  com- 
paring Figs.  114  and  129.  In  Fig. 

Fig.  130.     Tool  for  Turning  in  Brass  j  ^  jt  wm  be   ^^  ^  ^   ^ ^ 

of  the  work  is  outside  a  tangent  at  the  cutting  point  and  can  never 
interfere  with  the  bottom  of  the  tool.  In  Fig.  129,  the  surface  of 
the  work  is  inside  the  tangent,  and,  unless  the  tool  has  a  large 
amount  of  clearance,  it  will  cause  trouble  by  striking  the  concave 
surface. 


MACHINE  SHOP  WORK 


79 


Tools  for  brass  differ  from  those  used  on  steel  and  iron  in  that 
they  have  no  rake.  A  tool  suited  for  working  brass  is  shown  in 
Fig.  130.  Brass  does  not  readily  split,  and  the  chips  break  off  as 
soon  as  started  from  the  main  body.  When  turning  wrought  iron 
and  steel,  on  the  other  hand,  the  metal  does  not  break,  but  forms 
long  spiral  chips  if  the  tool  is  in  condition.  If  a  tool  with  top  rake 
is  used  in  turning  brass,  the  work  will  not  only  be  rough  in  appear- 


Fig.   131.     Common  Forms  of  Slide-Rest  Tools.      A— Left-Hand  Side;  B— Right-Hand  Side; 
C — Right-Hand  Bent;  D — Right-Hand  Diamond  Point;  E — Left-Hand  Diamond  Point; 
F — Round  Nose ;  G — Cutting -Off ;  H — Roughing ;  I — Threading ;  J — Bent  Thread-       / 
ing;  K — Boring;  L— Inside  Threading 

ance,  but  there  is  great  danger  of  the  tool  gouging  into  the  stock 
and  spoiling  the  work  or  tool,  possibly  both.  The  finishing  tools 
for  brass  may  be  square  or  round-nosed,  without  rake;  in  fact,  a 
small  amount  of  negative  rake  will  produce  a  much  better  surface. 
When  the  brass  contains  a  large  percentage  of  copper,  some  rake 
to  the  tool  may  be  required,  owing  to  the  ductility  and  toughness 
of  the  metal. 

Fig.  131  shows  common  lathe  tools  for  cast  iron  and  steel. 


80 


MACHINE  SHOP  WORK 


The  shape  of  the  tool  has  a  very  important  influence  on  the 
amount  of  work  it  can  be  made  to  do.  As  has  already  been  explained, 
these  shapes  vary  with  the  different  metals  that  are  being  worked, 
and  also  with  the  class  of  work  performed.  It  is  highly  important 
that  the  cutting  angles  be  correctly  formed.  While  hand-grinding 
on  the  emery  wheel  and  grindstone  is  fairly  satisfactory,  the  best 
results  can  be  obtained  only  by  the  use  of  a  regular  tool-grinding 


Fig.  132.     Tool-Grinding  Machine 

machine,  such  as  that  shown  in  Fig.  132.  In  addition  to  the  grind- 
ing, tools  for  fine  finishing  should  be  carefully  whetted  on  a  fine 
oil-stone. 

Cutting  Speed.  Importance  of  Speed  Element.  The  speed  at 
which  cutting  is  done  is  an  important  matter.  This  varies  with  the 
shape  of  the  tool,  the  quality  of  the  metal  being  worked,  and  the 
strength  of  the  lathe.  The  amount  of  metal  removed  in  a  given 


MACHINE  SHOP  WORK  81 

time  is,  therefore,  equally  variable.  It  is  impossible  to  make  a 
correct  estimate  of  the  time  that  a  given  piece  of  work  will  require, 
unless  all  of  the  above  elements  are  known.  For  approximate 
estimates,  the  cutting  speed  for  carbon  tool  steel  cutting  tools  may 
be  taken  to  range  about  as  follows: 

In  cast  iron  ........  „-'.'.  .  .from  30  to  40  feet  per  minute  \  . 

In  wrought  iron.  ./.  .....  from  25  to  30  feet  per  minute 

In  steel  .......  './.  .......  from  15  to  40  feet  per  minute 

In  brass  ....  ./.  .........  from  60  to  100  feet  per  minute 


Suppose  a  wpought-iron  shaft  6  feet  long  and  4  inches  in  diam- 
eter is  to  be  turned.  Let  the  lathe  be  capable  of  carrying  a  feed 
of  -£2  inch  per  revolution.  The  shaft  has  a  circumference  of 
4X3.1416  =  12.5664  inches.  To  give  the  tool  a  cutting  speed  of  25 

25x12 
feet  per  minute  the  shaft  must  make  ..  0  ,  AA  .  =  24  revolutions  per 


minute  (approximately),  giving  a  feed  of  j^X24  =  f  inch  in  that 
interval  of  time.  With  a  travel  of  f  inch  per  minute,  it  will  take  the 
cutting  tool  on  the  lathe  carriage  (6Xl2)-7-  J  =  96  minutes  to  take 
a  cut  the  whole  length  of  the  shaft. 

The  amount  of  feed  is  really  the  governing  element.  This  may 
be  as  much  as  3^  inch  per  revolution,  and,  for  finishing  cuts,  may 
not  be  more  than  T^TT  inch.  The  depth  of  the  tool  cut  also  influences 
the  time  required  to  finish  a  given  piece  of  work,  and  this  may  vary 
from  T¥7  to  |  inch,  depending  entirely  upon  the  shape  of  the  tool 
and  the  strength  of  the  lathe. 

Speeds  for  High-Speed  Steel.  The  cutting  speeds  given  above 
are  what  may  be  used  with  the  best  grades  of  tool  steel,  such  as 
Jessop's;  but  by  using  air-hardening  or  tungsten  steels,  the  speed 
of  cutting  may  be  very  much  increased  over  the  values  given  above. 
These  high-speed  steels  are  rapidly  coming  into  favor,  more  especially 
for  heavy  roughing  cuts. 

With  the  aid  of  these  steels,  the  cutting  speeds  have  been  in- 
creased, and  the  chip  is  made  heavier  in  both  depth  and  feed,  up  to 
the  point  where  the  lathe  refuses  to  carry  the  load.  The  ability  of 
this  quality  of  steel  to  stand  without  injury,  the  high  temperatures 
resulting  from  the  fast  feeding,  is  the  feature  which  enables  it  to 
perform  the  work  at  this  rate. 


82  MACHINE  SHOP  WORK 

For  what  are  now  known  as  the  high-speed  steel  tools,  the  speeds 
for  the  different  metals  mentioned  will  be  as  follows: 

Soft  cast  iron 50  to    80  feet 

Hard  cast  iron 20  to    40  feet 

Hard  cast  steel 30  to    40  feet 

Soft  machine  steel 60  to  120  feet 

Hard  machine  steel 20  to    45  feet 

Wrought  iron 35  to    45  feet 

T9ol  steel,  annealed 40  to    80  feet 

Tool  steel,  not  annealed 15  to    20  feet 

Soft  brass 110  to  130  feet 

Hard  brass : 90  to  110  feet 

Bronze 60  to    80  feet 

Bronze,  "gun  metal" 40  to    60  feet 

Gray  or  red  fiber 40  to    60  feet 

Usually  an  increase  in  speed  must  be  accompanied  by  a  reduc- 
tion in  the  feed — that  is,  in  the  number  of  revolutions  of  the  work 
per  inch  of  movement  of  the  tool.  The  following  directions  will  be 
proper  in  this  respect: 

Roughing  cuts  on  soft  cast  iron  may  be  made  with  a  feed  as  coarse  as  4  to 
5  per  inch,  with  a  strong  round-nosed  tool. 

Roughing  cuts  on  soft  machine  steel  forgings,  5  to  8  per  inch. 

Sizing  cuts  on  soft  cast  iron,  12  to  16  per  inch. 

Sizing  cuts  on  soft  machine  steel,  16  to  20  per  inch. 

Finishing  cuts  on  soft  cast  iron,  with  a  narrow-point  tool,  15  to  25  per 
inch. 

Finishing  cuts  on  soft  machine  steel,  with  a  narrow-point  tool,  20  to  40 
per  inch. 

Finishing  cuts  on  soft  cast  iron,  with  a  wide  point,  practically  a  straight- 
faced  tool  with  the  corners  slightly  rounded,  1  to  4  per  inch. 

Under  the  same  circumstances,  for  a  soft  machine  steel,  4  to  8  per  inch. 

Brass  will  be  turned  with  feeds  of  from  10  to  40  per  inch,  according  to  the 
kind  of  cut  and  shape  of  the  tool. 

Fiber  will  stand  a  heavy  feed  in  proportion  to  the  speed. 

Cooling  the  Tools.  For  cooling  the  tool  while  performing  heavy 
duty,  a  solution  of  sal  soda  is  preferable  to  water,  as  it  prevents 
rusting  of  the  work  and  machinery.  Its  office  is  simply  to  keep  the 
tool  cool.  If  a  tool  becomes  overheated,  the  edge  begins  to  turn 
over  and  it  becomes  dull. 

Referring  to  Fig.  116,  it  will  be  seen  that  the  chip,  as  it  is  being 
removed,  presses  down  on  the  top  face  of  the  tool.  This  pressure 
increases  with  the  depth  of  cut  and  the  feed.  The  resulting  friction 
would  soon  cause  a  high  temperature  in  the  tool  if  it  were  not 


MACHINE  SHOP  WORK 


83 


reduced  by  the  lubricant.  The  lubricant  cools  the  tool  by  absorb- 
ing a  portion  of  the  heat,  and  lessens  the  amount  of  heat  developed 
by  reducing  the  friction  between  the  tool  and  the  chip.  Clean, 
pure  water  is  the  only  lubricant  which  can  be  used  on  cast  iron; 
but  the  rapid  rusting  which  follows  its  use  makes  it  undesirable, 
and  as  a  result  cast  iron  is  usually  turned  dry.  Brass  is  also  usually 
turned  dry.  Prime  quality  lard  oil  is  sometimes  used  for  cooling 
the  tool;  but  the  greater  cost  prevents  its  extended  use/  unless 
some  means  are  provided  for  collecting,  separating,  and  filtering  it. 

LATHE    OPERATIONS 

Mounting  Work  on  Lathe.  Centering  Method.  A  piece  to  be 
turned  is  supported  on  the  two  centers  of  the  lathe.  In  order 
that  this  may  be  done,  it  is  prepared  by  drilling  and  countersinking 


Fig.  133.     Hole  and  Center  of  Correct 
Angle  for  Centering  Work 


Fig.  134.     Effect  of  Using  Different 
Angled  Hole  and  Center 


a  hole  in  each  end.  This  is  called  centering  the  work.  The  counter- 
sunk hole  should  have  the  same  angle  as  the  lathe  center  upon 
which  it  is  to  run.  The  hole  should  be  drilled  deep  enough  so  that 
the  point  of  the  lathe  center  may  not  strike.  The  shape  of  the  hole 
is  shown  in  Fig.  133.  The  generally  accepted  standard  angle  is  60 
degrees.  The  effect  of  using  a  60- degree  hole  on  a  90-degree  center 
is  shown  in  Fig.  134.  The  result  of  such  an  application  is  that  the 
bearing  will  be  concentrated  on  a  line  AB,  causing  rapid  wear  of  the 
outer  end  of  the  hole,  and  a  cutting  of  the  dead  center. 

The  size  of  center  holes  varies  with  the  weight  of  the  work  and 
the  character  of  the  operation.  Heavy  work  and  rough  turning 
require  large  center  holes,  while  small  work  and  fine  turning  can  be 
done  without  countersinking  deeply.  As  bearing  surfaces  in  cast 
iron  must  be  large  to  be  satisfactory,  center  holes  in  cast  iron  are 


84 


MACHINE  SHOP  WORK 


likely  to  give  trouble  by  unequal  and  rapid  wear.  When  heavy 
turned  work  in  cast  iron  must  be  very  accurate,  it  is  well  to  drill  a 
hole  in  each  end,  drive  in  a  plug  of  Wrought  iron  or  mild  steel,  and 
form  the  center  holes  in  the  plugs  thus  driven. 

When  the  piece  to  be  turned  has  been  put  in  place,  the  dead 
center  should  be  oiled  and  screwed  up  into  position.  It  should 
be  tightened  so  that  there  is  no  lost  motion,  and  yet  allow  the  work 
to  rotate  freely. 

Chuck  Method.  The  turning  of  shafts  and  bars  is  not,  however, 
the  only  kind  of  work  to  be  done  on  a  lathe.  Pieces  can  be  turned 


Fig.  135.     Work  Clamped  to  Faceplate 

that  are  thin,  that  have  holes  through  the  center,  or  which  are 
so  shaped  that  they  cannot  be  held  upon  the  centers.  In  such  cases 
it  becomes  necessary  to  hold  the  work  firmly  without  distortion. 
This  may  be  done  by  use  of  the  lathe  chuck. 

Faceplate  Method.  Still  another  method  of  holding  a  piece 
to  be  worked  is  that  shown  in  Fig.  135.  The  piece  is  clamped 
to  the  faceplate.  When  this  is  done,  there  should  be  a  bearing 
on  the  faceplate  immediately  beneath  the  clamping  strap.  For 
example,  consider  Fig.  136.  Suppose  a  disc  having  four  feet  on  one 
side  is  to  be  faced  off  on  the  front.  The  clamps  should  be  placed 
directly  over  the  feet,  as  in  B.  If  they  are  placed  between  the  feet 


MACHINE  SHOP  WORK 


85 


at  EE,  the  work  will  be  sprung  out  of  shape,  as  shown  by  the  dotted 
lines  in  A.  Then,  when  the  tool  has  done  its  work,  the  shape  of 
the  piece,  while  bolted  to  the  faceplate,  will  be  as  shown  in  C.  As 
soon  as  the  pressure  of  the  straps  is  removed,  the  elasticity  of  the 


Fig.  136.     Proper  and  Improper  Method  of  Clamping  Work 

metal  will  cause  the  piece  to  assume  the  convex  form  shown  in  D; 
whereas,  if  the  straps  had  been  placed  as  shown  in  B,  no  distortion 
would  have  been  produced. 

An  angle  iron  may  be  clamped  on  a   faceplate,  as  shown  in 
Fig.  137,   presenting  a  surface  parallel  to  the  lathe  axis,  to  which 


Fig.  137.     Angle  Iron  Clamped  to  Faceplate  and  Counterbalanced 

work  may  be  attached.  The  angle  irons  may,  of  course,  be  at  any 
angle  to  the  faceplate,  but  90  degrees  is  the  one  most  commonly 
used.  When  work  is  held  in  this  manner,  it  is  desirable  to  counter- 
balance it,  as  is  also  shown  in  Fig.  137, 


86 


MACHINE  SHOP  WORK 


Fig.  138.  Centering  a  Hollow  Piece 


Adjusting  Pieces  to  Center  on  Faceplate.  Whenever  a  piece 
is  to  be  turned  on  a  lathe  faceplate,  it  is  necessary  to  adjust  it  so 
that  its  rough  outline  is  approximately  concentric  with  the  lathe 
centers.  This  is  done  by  bolting  it  lightly  to  the  faceplate  and  run- 
ning the  lathe.  While  running,  a  piece 
of  chalk  is  held  so  that  the  projecting 
portions  will  strike  it.  This  marks  the 
piece,  and  indicates  the  part  that  is 
farthest  from  the  center.  The  lathe  is 
then  stopped,  and  the  piece  shifted, 
moving  the  chalk  mark  toward  the  lathe 
axis.  This  is  repeated  until  the  chalk 
makes  a  continuous  mark  around  the 
whole  circumference.  The  piece  may 
then  be  considered  to  be  centered. 

Suppose  it  is  necessary  to  center  a 
piece  having  a  hole  that  must  run  true.  In  this  case  the  inside  of 
the  hole  must  be  used  as  a  guide.  Let  Fig.  138  represent  the  hole 
with  the  thin  shell,  and  A  a  chalk  mark  made  as  described  for  cen- 
tering by  the  outside.  In  this  work  the  chalk  mark  must  be 
removed  away  from  the  axis.  A  lathe  tool  may  be  used,  as 
shown  in  Fig.  139,  to  center  a  piece  that  is  to  be  bored. 

Where  a  piece  has 
already  been  turned, 
greater  accuracy  is  de- 
manded, and  a  surface 
gage  may  be  used  to  ad- 
vantage. Set  the  gage  on 
the  bed  or  carriage  of  the 
lathe,  and  place  one  of  the 
points  in  contact  with  the 

work.  Rotate  the  work  as  before,  and  note  where  the  point  touches 
the  surface.  This  point  is  to  be  treated  in  the  same  way  as  the 
chalk  mark  explained  in  a  preceding  paragraph. 

A  still  more  accurate  method  of  positioning  a  piece  of  turned  work 
on  a  faceplate,  is  to  use  some  form  of  graduated  indicator,  such 
as  the  Starrett  indicator,  shown  in  Fig.  140.  This  is  held  in  the  tool- 
post,  the  contact-point  brought  against  the  work  until  the  indicating 


Fig.  139.     Use  of  Lathe  Tool  in  Centering  Piece 
to  Be  Bored 


MACHINE  SHOP  WORK 


87 


arm  is  at  zero.  If  the  work  is  now  slowly  rotated  by  hand,  the 
indicator  will  show  just  where  the  work  is  out  of  true,  and  being 
graduated  in  thousandths  of  an  inch,  will  also  show  how  much. 


Fig.  140.     Starrett  Indicator  Used  for  Centering  Work 

By  careful  adjustment,  the  piece  may  be  centered  to  the  degree  of 
accuracy  required. 

Instead  of  locating  a  cylindrical  surface  concentric  with  the  axis 
of  the  lathe,  it  often  happens  that  a  point  is  to  be  located  in  the 


Fig.  141.     Center  Tester 


axis.  For  this  purpose,  the  center  indicator,  Fig.  141,  is  used. 
The  free  end  of  the  short  arm  is  placed  in  the  point  to  be  centered 
(usually  a  prickpunch  mark),  the  fulcrum  being  held  in  the  tool- 


88 


MACHINE  SHOP  WORK 


post.  When  the  work  is  rotated,  the  free  end  of  the  long  arm 
not  only  shows  the  error,  but  magnifies  it  in  proportion  of  the  length 
of  the  short  arm  to  the  length  of  the  long  arm.  By  using  a  com- 
paratively long  arm,  the  point  can  be  very  closely  centered. 

Centering  Finished  Work.  After  making  the  center  punch 
mark  in  the  end  of  the  piece,  it  is  drilled  and  countersunk.  This 
must  be  done  very  accurately,  but  frequently  the  drilled  hole  or 
the  countersink  will  not  be  in  the  exact  center,  Fig.  142.  This 
may  be  caused  by  uneven  grinding  of  the  drill,  eccentric  motion  of 
the  drill  point  (due  to  the  inaccurate  running  of  the  spindle),  or 
the  distortion  of  the  metal  by  the  center  punch.  If  the  countersink 
is  not  exactly  in  the  center,  it  must  be  drawn  back  to  the  center. 


Fig.  142.     Countersink  off  Center 


Fig.  143.     Method  of  Drawing  the 
Hole 


This  is  generally  done  with  a  small  round-nosed  chisel  and  a  hammer. 
The  method  of  doing  this  is  as  follows:  After  making  the  center 
punch  mark,  the  hole  is  drilled  and  then  countersunk  slightly.  The 
work  should  now  be  stopped;  and  if  the  circumference  of  the  conical 
hole  is  not  concentric  with  the  circumference  of  the  piece,  a  groove 
should  be  cut  down  the  side  farthest  from  the  outer  circumference, 
as  shown  in  Fig.  143.  The  depth  of  the  groove,  which  should  be 
near  the  center,  depends  upon  the  amount  of  eccentricity.  The 
countersink  is  again  started,  and  the  groove  drilled  out.  If  the  circle 
is  not  yet  concentric,  the  process  is  repeated. 

Turning.  Facing  or  Squaring  Up.  The  first  operation  usually 
performed  on  a  piece  of  work  when  placed  in  the  lathe  is  facing 
or  squaring  up  the  ends.  This  must  be  done  to  get  a  uniform  bearing 
for  the  centers.  The  finishing  of  all  surfaces  at  or  nearly  at  right 
angles  to  the  axis  of  the  work,  is  classed  as  facing,  and  the  side  tool, 


MACHINE  SHOP  WORK 


89 


Fig.  123,  is  usually  employed.  For  roughing  cuts,  the  cutting 
face  of  the  tool  is  placed  at  a  slight  angle  to  the  work  surface,  in 
order  to  remove  the  metal  quickly;  but  for  finishing  cuts  it  is  placed 
nearly  flat  against  the  work,  so  that  a  light,  thin  chip  may  be  taken. 
Turning  a  Cylinder.  Turning  the  cylindrical  portions  of  the 
work  is  next  done  by  the  use  of  the  diamond  point  or  similar  tool. 
Roughing  cuts  are  taken  to  within  about  ^  inch  of  the  finished 
size,  and  a  fine  finishing  cut  reduces  the  work  to  the  exact  diameter. 
For  roughing  cuts  common  calipers  should  be  employed  for  test 
measurements;  while  for  finishing  cuts,  the  micrometer  caliper  is 
more  suitable.  All  measurements  must  be  taken  with  the  lathe  at 
rest,  as  motion  of  the  work  renders  close  calipering  impossible. 


; 


Fig.  144.    Turning  a  Taper  by  Setting  over  Dead  Center 

Turning  a  Taper.  It  frequently  happens  that  a  piece  must  be 
turned  tapering;  that  is,  one  end  is  to  have  a  greater  diameter  than 
the  other.  There  are  three  ways  of  accomplishing  this  result:  (a) 
setting  over  the  dead  center,  (b)  the  use  of  the  compound  res^j, 
and  (c)  the  use  of  the  taper  attachment. 

Setting  over  Dead  Center.  Setting  the  dead  center  over  is  the 
more  common  method.  Provision  is  generally  made  for  moving 
the  dead  center  laterally  toward  the  front  or  rear  of  the  bed  accord- 
ing to  the  taper  required.  With  the  dead  center  set  over,  the 
tool  will  be  at  unequal  distances  from  the  live  and  dead  centers, 
because  its  movement  is  parallel  to  the  axis  of  the  lathe.  This 
is  shown  in  Fig.  144.  The  piece  to  be  turned  is  placed  upon  the 
centers  A  and  B,  and  the  dead  center  is  moved  from  the  axis  a 
distance  equal  to  the  difference  between  the  radii  AD  and  EC. 


90  MACHINE  SHOP  WORK 

This  leaves  the  side  DC  parallel  to  the  center  line  of  the  lathe;  hence 
the  tool  will  be  fed  along  this  line.  The  objection  to  doing  work 
by  this  method  is  that  the  lathe  centers  do  not  have  full  bearings 
at  the  ends  of  the  work,  and  the  center  holes  are  likely  to  wear  out 
of  their  true  positions. 

If  the  taper  is  to  be  turned  on  a  piece  held  by  a  mandrel,  or  if 
the  taper  is  to  extend  but  a  part  of  the  total  length  of  the  work,  the 
amount  of  set-over  for  the  dead  center  must  be  calculated  in  the 
same  manner  as  though  the  taper  were  to  extend  the  whole  length  of 
the  mandrel  or  work.  In  other  words,  the  amount  of  set-over  for 
the  dead  center  is  determined  by  the  distance  between  the  centers 

and  the  rate  of  taper. 

For  example :  Suppose 
the  mandrel  in  Fig.  145  to 
be  16  inches  long;  and  the 
piece  of  work  CD,  which 
is  to  be  turned  tapering, 
is  4  inches  long;  suppose 
also  that  the  diameter  at 

Fig.  145.      Turning  Taper  on  Piece  Held  by  Mandrel         -^   .  ,        ,    .       ,  „ 

D  is  to  be  J  inch  smaller 

than  at  C.  Then,  for  one  inch  of  length,  the  difference  in  diam- 
eters would  be  one-fourth  of  \  inch,  or  yg-  inch;  and  for  a  length 
of  16  inches,  it  would  be  sixteen  times  xg-  inch,  or  1  inch.  Since  the 
set-over  is  equal  to  the  difference  of  the  radii,  the  set-over  for  the  16 
inches  wrould  be  one-half  of  1  inch,  or  \  inch.  This,  then,  would  be 
the  set-over  for  the  work  under  consideration,  and  for  any  piece  to 
be  tapered  at  the  rate  of  J  inch  in  4  inches  when  held  on  a  16-inch 
mandrel.  In  accurate  work,  the  distance  to  which  the  centers 
enter  the  mandrel  must  be  considered. 

The  machinist  generally  sets  over  the  dead  center  as  accurately 
as  possible  and  takes  a  roughing  cut.  The  taper  is  then  tested  by 
a  careful  comparison  of  the  diameters,  or  by  trying  it  in  a  tapered 
hole  of  the  proper  angle,  and  setting  the  center  more  accurately. 
Setting  over  the  dead  center  does  not  give  accurate  results,  on 
account  of  the  fact  that  the  centers  do  not  have  a  true  bearing  at 
the  ends  of  the  work.  Naturally,  the  shorter  the  work,  compared 
with  the  amount  of  set-over,  the  greater  the  inaccuracy  because  of 
the  greater  nearness  of  the  centers. 


MACHINE  SHOP  WORK 


EXAMPLES  FOR  PRACTICE 


91 


1.  A  tapered  bushing  3  inches  long  and  of  4  and  4J  inches 
outside  diameters,  is  driven  on  a  12-inch  mandrel  for  turning.     How 
much  must  the  dead  center  be  set  out  of  line  in  order  to  do  the  work? 

Ans.     1  inch 

2.  A  connecting  rod  6  feet  long  is  to  be  turned  tapering  from 
the  center  to  the  neck  back  of  the  stub  ends.     This  distance  is  26 
inches.     The  diameter  at  the  center  is  to  be  3  inches,  and  at  the  neck 
2J  inches.     How  much  offset  must  be  given  to  the  dead  center? 

Ans.     .692+ inch 

3.  A  shaft  "had  a  taper  2  feet  long  turned  on  one  end.     The 
large  end  of  the  taper  was  4  inches  in  diameter,  and  the  small  end  was 


Fig.  146.     Compound  Tool  Slide 

3  inches  in  diameter.  The  dead  center  was  set  over  1  inch.  How 
long  was  the  shaft?  Ans.  4  feet 

Compound  Slide.  In  turning  a  taper  with  the  compound  slide, 
the  work  may  be  held  in  a  chuck,  on  the  faceplate,  or  between 
the  centers.  The  compound  slide,  Fig.  146,  is  then  set  at  such  an 
angle  that  the  direction  of  motion  of  the  tool  will  coincide  with  the 
required  taper.  Several  methods  are  employed  for  this  adjustment 
cf  the  rest.  The  tool  is  fed  to  the  work  by  means  of  the  feed-handle 
A  attached  to  the  compound  slide. 

Taper  Attachment.  The  taper  attachment,  Fig.  147,  is  in  the 
form  of  a  guide  which  is  bolted  to  the  back  of  the  lathe.  It  can  be 
set  at  any  desired  angle  with  the  axis  of  the  lathe,  the  limit  usually 


92  MACHINE  SHOP  WORK 

being  a  taper  of  about  three  inches  per  foot.  The  guide  is  graduated 
so  that  calculations  based  on  the  length  of  the  work  are  unnecessary. 
A  slide  moving  with  the  guide  is  attached  to  the  cross-feed  slide 
of  the  carriage.  This  cross-feed  slide  is  loosened,  and,  while  the 
carriage  is  moved  by  the  feeding  mechanism,  the  tool  is  moved 
in  or  out  according  to  the  direction  of  the  taper. 

One  of  the  important  points  to  be  observed  in  turning  tapers, 
is  to  have  the  cutting  point  of  the  tool  exactly  level  with  the  work 
axis.  If  this  is  not  done,  the  work  will  not  be  truly  conical,  and  the 
rate  of  taper  will  vary  with  each  succeeding  cut. 

In  case  an  internal  and  an  external  taper  are  to  be  turned  so 
as  to  form  a  fit,  the  internal  taper  should,  if  the  character  of  the 


Fig.  1 17.     Taper  Attachment 

work  will  permit,  be  made  first.  After  this  has  been  done,  the  ex- 
ternal taper  should  be  turned  and  tested  several  times  during  the 
process.  The  external  taper  is  first  turned  as  accurately  by  meas- 
urement as  possible,  taking  care  that  the  piece  is  made  a  trifle  large. 
Draw  a  chalk  line  on  the  external  taper,  from  one  end  to  the  other; 
press  the  tapers  together,  and  give  one  of  them  a  slight  twist.  On 
separating  the  tapers,  the  rubbing  of  the  chalk  will  show  where 
the  work  was  in  contact,  and,  by  resetting  the  lathe  and  repeating 
the  process,  a  very  accurate  fit  can  be  obtained. 

Turning  Shafting.  Shafting  is  usually  turned  T§-  inch  less 
than  the  nominal  diameter.  For  instance,  instead  of  a  shaft  2 
inches  in  diameter,  one  of  1  if  inches  in  diameter  is  used.  The 
reason  is  that  iron  of  a  nominal  diameter  of  2  inches,  usually  yj 


MACHINE  SHOP  WORK  93 

jnch  over  size,  can  be  used.  Before  turning  a  length  of  shafting, 
the  rough  bar  should  be  carefully  straightened.  After  the  center 
holes  have  been  drilled  and  the  piece  placed  in  the  lathe,  the  work 
can  be  rotated,  and  the  eccentric  portions  marked  with  chalk. 
When  this  has  been  done,  the  bar  should  be  removed  from  the 
lathe  and  sprung  back  into  true  alignment.  It  is  well  to  take  two 
cuts  in  finishing  shafting,  one  for  the  roughing  cut,  and  one  very 
fine  finishing  cut.  The  tool  for  the  latter  part  of  the  work  should 
be  kept  flooded  with  oil  or  with  a  solution  of  sal  soda.  If  the  work 
.is  light,  a  tool  holder,  carrying  both  the  roughing  and  the  finishing 
tools,  may  be  used.  This  makes  it  possible  to  do  the  work  in  prac- 
tically the  same  time  as  for  one  cut. 

Preventing  Spring  in  Shafting.  As  a  length  of  shafting  is  likely 
to  spring  under  the  pressure  of  the  tool,  some  method  of  preventing 
such  action  must  be  employed.  A  center  rest  can  be  used.  It 
is,  however,  inconvenient,  and  must  be  frequently  moved,  or  at  times 
it  will  stand  too  far  from  the  tools.  Furthermore,  as  the  rough 
bar  will  neither  be  truly  round  nor  concentric  with  the  centers, 
it  is  necessary  to  turn  spots  for  the  center  rest.  Spotting,  however, 
takes  considerable  time,  owing  to  the  fact  that  very  light  cuts  must 
be  taken  in  order  to  avoid  springing  the  bar.  A  good  method 
is  to  have  a  ring  attached  to  the  tool  holder;  the  internal  diameter 
of  this  ring  is  that  of  the  finished  shaft.  It  is  slipped  over  the  tail- 
stock  center,  and  follows  the  finishing  tool.  It  must,  of  course, 
be  rigidly  fastened  to  the  tool  holder.  In  this  way  the  shaft  is  sup- 
ported close  to  the  tools;  the  ring  also  serves  as  a  gage  to  measure 
the  diameter  of  the  shaft.  If,  for  any  reason,  the  tools  turn  to  a 
larger  diameter  than  the  inside  of  the  ring,  notice  is  immediately 
served  upon  the  workmen  to  that  effect,  by  binding  in  the  ring. 

Eccentric  Turning.  The  term  "eccentric'*  is  given  to  a  rotating 
machine  part  which  is  used  to  "throw"  a  mechanism  eccentric 
with  its  main  center  line.  Eccentrics  may  be  said  to  include  all 
crank  motions,  also  many  cam  motions.  In  general  shop  terms, 
however,  an  eccentric  is  a  machine  part  having  an  outer  circle 
which  is  off  center  or  eccentric  with  its  shaft. 

In  construction  it  may  be  machined  as  a  part  of  its  own  shaft, 
or  it  may  be  so  made  as  to  slip  onto  a  shaft  in  which  case  provision 
must  be  made  for  keying  it  to  the  shaft. 


94 


MACHINE  SHOP  WORK 


Throw  of  Eccentric.  The  throw  of  an  eccentric  may  be  taken 
as  the  radius  of  eccentricity  or  it  may  He  taken  to  mean  twice  the 
radial  eccentricity. 

Machining  Eccentrics.  While  eccentrics  may  be  machined  in 
a  variety  of  ways,  the  accompanying  text  will  consider  the  lathe 


Fig.  148.     Machining  Crank  Shaft 

only.  If  the  eccentric  is  of  the  simple  form  of  two  circles  with 
their  centers  offset  in  relation  to  each  other,  the  work  must  be  done 
on  a  mandrel  provided  with  two  sets  of  centers,  one  pair  for  each 
circle,  Fig.  149. 

Eccentric  Solid  with  Shaft.  In  this  case  if  the  throw  of  the 
eccentric  is  less  than  the  radius  of  the  shaft,  both  sets  of  work  cen- 
ters may  be  made  in  the  shaft  ends.  Where 
the  throw  is  too  great  to  allow  this,  some  pro- 
vision must  be  made  for  the  second  set  of 
centers. 

Two  methods  for  doing  this  are  in  com- 
mon use,   (a)  casting  or  forging  lugs  upon 
each  end  of  the  shaft  sufficiently  large  to  in- 
clude the  needed  centers,  (b)  use  of  attach- 
ments for  the  shaft  ends,  the  attachments  them- 
selves being  provided  with  the  desired  centers. 
Eccentrics  Not  Solid  with  Shaft.    Eccentrics  of  this  sort  are 
usually  those  which  have  a  hole  chucked  through  their  center  of 
throw.    Such  eccentrics  are  usually  finished  upon  mandrels  having 
two  sets  of  centers.     Fig.  150  shows  such  a  mandrel.    Work  centers 


Fig.  149.     General  Shape  of 
Eccentric 


MACHINE  SHOP  WORK 


95 


A  and  Af  are  those  to  be  used  while  the  throw  surfaces  are  being 
machined.  B  and  Bf  the  centers  used  while  constructing  the  man- 
drel. With  such  a  mandrel  as  this  driven  into  the  provided  hole, 


Fig.  150.     Mandrel  for  Holding  an  Eccentric 

work  can  be  done  upon  surfaces  which  are  concentric  to  the  axis 
of  the  mandrel  or  which  are  eccentric  with  it. 

Using  a  Faceplate  or  Work  Chuck.  Eccentrics  can  and  often 
are  machined  by  mounting  them  upon  a  suitable  faceplate  or  by 
holding  the  work  in  a  suitable  chuck.  Previous  to  mounting 
the  work  upon  the  faceplate  for  eccentric  turning,  it  is  usual  to 
face  off  a  surface  to  set 
squarely  on  the  front  face 
of  the  plate,  as  in  Fig.  151. 

Crank-Shaft  Turning. 
This  is  a  special  kind  of 
eccentric  turning  in  which 
the  throws  are  termed 
crank  pins  and  the  remain- 
ing bearings  are  the  shaft 
proper.  In  Fig.  148  is 
shown  a  simple  crank  shaft 
with  a  crank  pin  G  and 
regular  bearings  CD. 

It  is  customary  to 
rough  turn  the  bearings 
C  and  D  previous  to  ma- 
chining the  crank-pin  bearing  G.  The  order  of  operations  is  as 
follows:  Locate,  drill,  and  ream  work  centers  in  ends  A  and  B. 
Square  ends  A  and  B  to  the  correct  overall  length.  Rough  turn 
C  and  D.  Rough  square  E  and  F.  Place  attachments  K  and 
K  on  the  ends  of  bearings  C  and  D  in  position  to  machine  crank- 
pin  bearing  G  as  shown.  Rough  turn  G.  Rough  and  finish  square 


Fig.    151.     Piece  Mounted  on  Faceplate  for 
Eccentric  Turning 


96  MACHINE  SHOP  WORK 

H  and  /  to  gap  dimensions.  Finish  surface  (2  to  dimensions. 
Remove  attachments  K  and  K  and  with  work  again  mounted  on 
centers  A  and  B,  finish  square  surfaces  E  and  F,  and  finally  finish 
to  accurate  dimensions  surfaces  C  and  D. 

Attachments  K  and  K.  These  are  often  known  as  jigs  and  are 
made  and  used  in  a  variety  of  forms.  Those  shown  in  Fig.  148  ; 
are  suitable  for  a  single-throw  crank,  while  those  used  in  turning 
or  grinding  multiple-throw  cranks  may  be  circular  in  form  and 
provided  with  several  wrork  centers.  In  all  cases  it  means  simply 
the  provision  of  work  centers  opposite  to  and  in  alignment  with  the 
surface  to  be  machined.  It  is  self-evident  that  the  same  results 
can  be  obtained  by  casting  or  forging  lugs  or  flanges  upon  the  ends 
suitable  for  the  various  work  centers. 

Handling  Shaft  Surfaces.  In  turning  surfaces  C  and  D,  if  the 
shaft  is  slender  or  of  considerable  length,  use  a  center  rest  on  surface 
D  while  working  surface  C,  to  assist  in  its  support  and  reverse  for 
surface  D. 

If  necessary,  struts  may  be  placed  between  the  jigs  and  cheeks 
of  the  shaft  while  machining  surface  G.  In  this  manner,  the  whole 
piece  may  be  steadied  somewhat. 

Drive  the  work,  when  surfaces  C  and  D  are  being  machined, 
with  a  common  lathe  dog.  Use  some  sort  of  a  faceplate  stud  when 
machining  surfaces  E,  F,  and  G. 

Boring  Bars.  The  boring  of  holes  sometimes  calls  for  a  length 
and  strength  of  tool  that  cannot  be  readily  attained  with  the  ordi- 
nary boring  tool.  A  great  deal  of  such  boring  is  done  with  double- 
headed  tools.  These  tools  are  held  in  bars,  and  cut  at  each  end. 
An  ordinary  form  of  such  tool  is  shown  in  Fig.  152.  The  tool  A 
is  turned  and  fitted  so  that  when  placed  in  the  bar  it  is  central  with 
the  centers  of  the  latter.  It  is  held  in  position  by  the  key  B.  It 
cuts  at  each  end.  Such  a  tool  may  be  made  to  do  very  rapid  work. 
It  is  extensively  used  for  boring  in  places  where  a  piece  of  work 
must  be  duplicated  a  great  number  of  times. 

Tools  of  this  kind  are  also  used  for  finishing.  After  the  cut 
has  been  started,  the  tool  should  not  be  stopped  until  the  cut  has 
been  completed.  If  it  is  stopped,  there  will  be  a  ledge  in  the  bore 
at  that  point.  The  reason  for  this  is  found  in  the  springing  of  the 
metal  and  the  contraction  due  to  cooling  while  at  rest.  The  tools 


MACHINE  SHOP  WORK 


97 


used  for  finishing  usually  have  a  broad  surface.  Those  used  for  the 
roughing  cut  are  narrower;  they  wear  more  rapidly  than  the  finishing 
tools,  and  are  usually  adjustable.  An  excellent  example  of  the  use 
of  boring  bars  is  found  in  the  boring  of  engine  cylinders.  Special 
machines  are  used  for  such  work.  The  greater  portion  of  the  work 
is  done  with  a  boring  bar  such  as  that  shown  in  Fig.  153.  It  con- 
sists of  a  heavy  bar  A,  upon  which  there  is  a  stiff  traveling  head  B. 


Fig.  152.     Boring  Bar 


The  latter  carries  the  tool  C,  which  may  or  may  not  be  capable  of  a 
transverse  adjustment.  The  head  moves  longitudinally  on  the 
bar,  and  is  held,  adjusted,  and  fed  by  the  screw  D.  At  one  end 
of  the  screw,  there  is  a  star  wheel  E,  by  which  it  is  turned.  As  the 
bar  revolves,  one  arm  of  the  star  strikes  against  a  stop  F  at  each 
revolution.  This  turns  the  screw  by  an  amount  proportional  to  the 
number  of  arms  in  the  star.  For  example,  if  there  are  six  arms 


Fig.  153.     Special  Boring  Bar  for  Boring  an  Engine  Cylinder 

in  the  star,  the  latter  will  be  turned  one-sixth  of  a  revolution  for 
each  revolution  of  the  boring  bar.  As  the  screw  turns,  it  moves 
the  head  along  the  bar  by  an  amount  proportional  to  the  pitch  of 
its  thread  and  "the  arms  in  the  star.  This  forms  the  feed  of  the  tool, 
For  example,  if  a  star  has  four  arms,  and  is  keyed  to  a  screw  of  eight 
threads  to  the  inch,  then,  for  each  revolution  of  the  bar,  the  head 
will  be  advanced  ^  of  an  inch.  Another  form  of  boring  bar  is 
shown  in  Fig.  154. 


98 


MACHINE  SHOP  WORK 


Boring  bars  with  fixed  tools  are  also  used.  In  such  cases  the 
work  is  caused  to  travel  beneath  the  bar  as  it  is  turned.  A  case  of 
this  kind  occurs  in  the  boring-out  of  brasses  for  railroad  cars. 

In  general,  it  may  be  stated  that  all  heavy  work  should'  be 
machined  in  the  position  which  it  is  eventually  to  occupy.  This  is 
to  overcome  its  tendency  to  spring  out  of  shape  under  the  influence 
of  its  own  weight.  In  small  articles  this  tendency  is  inappreciable. 
For  large  pieces  it  is  sometimes  quite  apparent. 

Screw  Cutting.  The  tools  used  for  cutting  threads  are  called 
screw-cutting  tools.  These  tools  are  used  in  the  lathe  in  the  same 


Fig.  154.    Boring  Head 

manner  as  the  diamond-point  and  round-nosed  tools.  The  cutting 
edge  of  the  tool  must  be  of  the  same  contour  as  the  space  between 
the  finished  threads. 

Types  of  Threads.  There  are  five  types  of  screw-threads 
commonly  used  in  this  country:  the  V-thread,  shown  in  Fig.  155, 
has  the  form  of  an  equilateral  triangle,  with  an  angle  of  60  degrees. 
It  is  sharp  at  the  top  and  bottom.  This  thread  is  difficult  to  cut, 
because  of  the  trouble  experienced  in  keeping  the  point  of  the  tool 
sharp. 

The  Sellers,  Franklin  Institute,  or  United  States  Standard 
is  a  modified  form  of  V-thread,  shown  in  Fig.  156.  This  thread 
has  an  angle  of  60  degrees,  with  the  top  and  bottom  flattened  for 
one-eighth  of  its  depth. 


MACHINE  SHOP  WORK 


99 


Another  form  in  common  use  is  the  square  thread,  shown  in 
Fig.   157.     The  thread  and  space  are  of  the  same  width.    This 


Fig.  155.     Section  of  V-Thread 


Fig.   156.     Sellers,  Franklin  Insti- 
tute, or  United  Stated  Standard 
Thread 


thread  is  used  where  heavy  work  is  done,  such  as  in  jack-screws 
and  presses. 

The  Whitworth  thread  is  similar  to  the  United  States  Standard, 
the  slight  differences  being  as  follows:  the  sides  form  an  angle  of 
55  degrees  instead  of  60  degrees,  and 
the  top  and  bottom  are  rounded  instead 
of  flat. 

The  fifth  type,  the  Acme  thread,  is 
somewhat  similar  to  the  square  form. 
The  difference  is  that  the  sides  incline 
14J  degrees  from  those  of  the  square 
thread.  This  form  of  thread  is  much  used  for  lathe  lead-screws  and 
for  giving  motion  to  sliding  parts  of  fine  instruments,  because  the 
thread  is  simpler  to  construct  than  the  square  form,  and  the  lost 


Fig.  137.     Square  Thread 


Fig.  158.     Side  View  of  Tool  for 
Cutting  Square  Threads 


Fig.  159. 
Square  Thread 
Tool     Showing 
Inclination      of 
Thread  to  Body 


motion  can  be  taken  up  by  simply  closing  the  nut  halves  nearer 
together. 

Cutting  Tool  for  Square  Threads.    The  tool  used  for  cutting 
square  threads  is  shown  in  Figs.  158  and  159.     It  is  of  the  proper 


100 


MACHINE  SHOP  WORK 


TABLE  III* 
U.  S.  Standard  Threads,  Bolts,  and  Nuts 

The  Tap  Drill  Diameters  in  the  Table  Provide  for  a  Slight  Clearance  at  the  Root  of  the  Thread 

in  Order  to  Facilitate  Tapping  and  Reduce  Tap  Breakages.     If  Full  Threads  Are  Required 

Use  the  Diameters  at  the  Root  of  the  Threads  for  the  Tap  Drill  Diameters  Instead. 

U.  S.  STANDARD  SCREW  THREAD 
1 


Pitch  =  -srs — ._ 

No.  of  Th  as.  per  Inch 

Depth  of  Th'd.  =  0.6495  X  Pitch 


Widthof  Flat  = 


Pitch 


H 

DIMENSIONS  OP  NUTS 

a 

AREA  IN 

1 

H 

o 

AND  BOLT  HEADS 

PS 

h 

ft 

-.  2 

SQUARE  INCHES 

B 

05  td 

H 

w  Q 

H        pi   c 

5     "IS  c 

t-t 

NUMBEI 
THREAI 
PER  INC 

III 

If 

jjif 

I||] 

Fo] 

<2>i 

^ 

1 

H 

of 

at  Root 

Bolt 

of 
Thread 

11?  I 

(cT 

U  -1 

D°u 

l 

20 

0.185 

it 

0.049 

0.026 

160 



i 

0.578 

0.707 

i 

4 

i 

TS 

18 

0.240 

JL 

0  076 

0.045 

270 

19 

0.686 

0  840 

|| 

f 

16 

0.294 

4 

0.110 

0  068 

410 

11 

0.794 

0.972 

t 

& 

14 

0.345 

23 

0.150 

0.093 

560 

25 

0.902 

1.105 

A 

11 

1 

13 

0.400 

II 

0.196 

0.126 

760 

|2 

1.011 

1.237 

i 

•A 

A 

12 

0.454 

15. 

0.248 

0.162 

1000 

3JL 

1.119 

1.370 

iir 

.3i 

f 

11 

0.507 

il 

0.307 

0.202 

1210 

260 

iS 

.227 

1.502 

il 

3. 

4 

10 

0.620 

£i 

0.442 

0.302 

1810 

680 

H 

.444 

1.768 

| 

| 

1 

9 

0.731 

^ 

0.601 

0.419 

2520 

1210 

1A 

.660 

2.033 

1 

ft 

1 

8 

0.838 

M 

0.785 

0.551 

3300 

1790 

if 

.877 

2.298 

T6 

H 

7 

0.939 

•fi 

0.994 

0.694 

4160 

2470 

lit 

2.093 

2.563 

1| 

IT 

H 

7 

.064 

1A 

1.227 

0.893 

5350 

3470 

2 

2.310 

2.828 

H 

1 

U 

6 

.158 

1.485 

1.057 

6340 

4260 

2A 

2.527 

3.093 

if 

1^ 

H 

6 

.283 

\ii 

1.767 

1.295 

7770 

5500 

21 

2.743 

3.358 

1A 

if 

5| 

1.389 

W 

2.074 

1.515 

9090 

6630 

2A 

2.960 

3.623 

if 

1A 

if 

5 

.490 

117 

2.405 

1.746 

10470 

7830 

21 

3.176 

3.889 

if 

H 

if 

5 

1.615 

Ifi 

2.761 

2.051 

12300 

9470 

2ff 

3.393 

4.154 

8^ 

2 

4| 

1.711 

If 

3.142 

2.302 

13800 

10800 

3i 

3.609 

4.419 

2 

1A 

2| 

4£ 

1.961 

3.976 

3.023 

18100 

14700 

3| 

4.043 

4.949 

2? 

2* 

4 

2.175 

2M 

4.909 

3.719 

22300 

18500 

3| 

4.476 

5.479 

i" 

2f 

4 

2.425 

2fj 

5.940 

4.620 

27700 

23600 

4.909 

6.010 

2l 

2*5* 

3 

3^ 

2.629 

2r& 

7.069 

5.428 

32500 

28000 

4j 

5.342 

6.540 

3 

3| 

3f 

2.879 

2ff 

8.296 

6.510 

39000 

34100 

5 

5.775 

7.070 

3i 

2|6 

3^ 

3j 

3.100 

3^z 

9.621 

7.548 

45300 

40000 

5| 

6.208 

7.600 

3£ 

2ri 

3| 

3 

3.317 

3f 

11.045 

8.641 

51800 

45000 

5| 

6.641 

8.131 

3f 

2| 

4 

3 

3.567 

3f 

12.566 

9.963 

59700 

50100 

6| 

7.074 

8.661 

3A 

4| 

2| 

3.798 

3||. 

14.186 

11.340 

68000 

58000 

Qi 

7.508 

9.191 

4| 

2f 

4.028 

4^. 

15.904 

12.750 

76500 

66000 

6f 

7.941 

9.721 

3^ 

4§ 

2f 

4.255 

4ir 

17.721 

14.215 

85500 

74000 

71 

8.374 

10.252 

4f 

3f 

5 

4.480 

4^. 

19.635 

15.760 

94000 

82500 

7f 

8.807 

10.782 

5 

3H 

5j 

2| 

4.730 

A  13 

21.648 

17.570 

105500 

93000 

8 

9.240 

11.312 

5| 

4 

5^ 

2f 

4.953 

5JL. 

23.758 

19.260 

116000 

103000 

8f 

9.673 

11.842 

4^ 

5f 

2f 

5.203 

5^. 

25.967 

21.250 

127000 

114000 

8f 

10.106 

12.373 

5| 

4|9 

6 

2! 

5.423 

5| 

28.274 

23.090 

138000 

124000 

9| 

10.539 

12.903 

6 

*  Reprinted  from  Machinery. 


MACHINE  SHOP  WOR.  ;  101 


thickness  at  the  cutting  edge,  but  is  somewhat  ^nat/c^ejr.'bf-Xjk^f  this 
point.  The  sides  of  the  tool  are  inclined  to  the  body/asJsh"oWn  at 
AB,  Fig.  159;  the  amount  of  this  inclination  varies  with  the  pitch  of 
the  thread  and  the  diameter  of  the  piece  on  which  the  thread  is  to 
be  cut.  To  find  the  inclination,  draw  an  indefinite  straight  line  A  B; 
and  at  right  angles  to  it  draw  ^  ^ 

CD,  Fig.  160.  Make  the  length  JT 
of  CD  equal  to  the  circumfer- 
ence of  the  thread  to  be  cut, 
measured  at  the  root  of  the 
thread.  On  AB,  lay  off  from 
C  a  distance  EC  equal  to  the 
pitch;  then  draw  ED.  This  line 
will  represent  the  angle  of  the 

.  ,         „      ,  ,  ,         .—.,  Fig.  160.     Diagram  of  Clearance  Angle 

side  of  the  thread.     The  angle 

of  the  side  of  the  cutting  tool  must  be  a  little  greater  for  clearance. 

Cutting  Tool  for  Inside  Threads.  For  cutting  inside  threads, 
fhe  shape  of  the  cutting  edge  of  the  tool  should  be  the  same  as  for 
cutting  an  outside  thread,  and  the  tool  must  be  made  so  that  the 
cutting  edge  alone  touches  the  work.  This  is  accomplished  by 
bending  the  tool  as  shown  in  Fig.  161,  and  giving  it  considerable 
clearance. 

Cutting  Standard  Screw-  Threads.  When  screw-threads  are  to 
be  cut,  the  pitch  used  depends  upon  the  outside  diameter  of  the 
bar.  A  standard  which  has  been  gen- 
erally adopted  in  the  United  States, 
is  known  as  the  United  States  Stand- 
ard. Table  III  gives  the  outside 
diameter  of  the  screw  from  J  inch  to 

6  inches  in  diameter,  with  the  num-       rig  J61    Iatml  Threa<Ung  Too, 
ber  of  threads  per  inch  to  be  cut. 

When  setting  the  tool  for  any  form  of  thread,  the  tool  point 
must  be  exactly  level  with  the  work  axis,  and  a  line  at  right  angles 
to  the  axis  of  the  lathe  must  bisect  the  angle  of  the  tool  point.  In 
order  that  these  conditions  may  be  fulfilled,  a  thread  or  center  gage, 
Fig.  162,  is  used.  In  this  tool,  the  angles  A,  B,  and  C  are  made 
exactly  60  degrees.  The  two  opposite  sides  are  parallel.  The 
angles  A,  B,  and  C  are  used  when  grinding  and  setting  the  tool. 


102 


.MACHINE  SHOP  WORK 


The  sides  of  t he  former  are  made  to  touch  all  along  the  edge  of  the 
tool.  For  setting  the  tool,  the  upper  parallel  side  is  held  against 
the  face  of  the  work  in  a  horizontal  position.  The  tool  is  then 
set  so  that  its  sides  touch  along  the  edges  of  the  notch  B.  The 

angle  C  may  be  used  to  gage  the 
thread  after  it  is  cut. 

The  pitch  measurement  of 
fine  threads  is  a  difficult  matter 
where  an  ordinary  rule  is  used 

Fig.  162.     Thread  or  Center  Gage  1,1,1  i     i  ,1-1 

and  the  threads  between  the  inch 

marks  are  counted;  for  this  purpose  pitch  gages,  Fig.  163,  are  very 
often  used.  The  gages  are  short  screw-sections  on  thin  sheets  of 
metal.  To  ascertain  the  pitch  of  any  thread,  set  the  gages  over 
it  successively  until  one  is  found  that  exactly  fits.  The  figures 
stamped  thereon  will  give  the  number  of  threads  per  inch. 

Lathe  Adjustment  for  Cutting  Threads.  The  cutting  of  a  thread 
demands  that  there  shall  be  a  certain  definite  ratio  of  motion  between 
the  rotation  of  the  work  and  the  travel  of  the  carriage.  For  example> 
if  a  screw  having  a  pitch  of  J  inch — or  with  four  threads  to  the  inch, 
as  it  is  usually  stated — is  to  be  cut,  the  work  spindle  must  make  four 
revolutions  while  the  carriage  is  moving  one  inch  along  the  bed. 

If  the  screw  is  to  have 
eight  threads  per  inch, 
the  work  spindle  must 
make  eight  revolutions 
to  each  inch  of  motion  of 
the  carriage  or  tool;  if  six 
threads,  then  six  revolu- 
tions to  the  inch  of 
motion,  etc. 

If,  then,  the  apron 
lead-screw  has  four 
threads  to  the  inch,  it 
is  evident  that  the  speed 

of  rotation  of  the  spindle  and  of  the  screw  must  be  the  same, 
in  order  to  cut  a  screw  of  four  threads  to  the  inch.  In  other 
words,  for-  each  revolution  of  the  lead-screw,  the  carriage  moves 
the  distance  of  the  pitch  of  the  same,  or  J  inch.  Hence  the  gears 


Fig.  163.     Screw  Pitch  Gage 


MACHINE  SHOP  WORK  103 

J  and  L,  Fig.  95,  must  have  the  same  number  of  teeth.  When 
a  screw  of  eight  threads  per  inch  is  to  be  cut,  the  spindle  must 
make  twice  as  many  revolutions  as  the  lead-screw.  Then,  for 
each  revolution  of  the  spindle,  the  lead-screw  makes  half  a  revolution, 
and  thus  moves  the  carriage  J  inch.  In  this  case,  the  screw  gear  L 
must  have  twice  as  many  teeth  as  the  stud  gear  J.  For  six  threads, 
the  ratio  of  revolutions  between  spindle  and  screw  is  1J  to  1.  This 
requires  1J  times  as  many  teeth  in  the  screw  gear  L  as  in  the  stud 
gear  J. 

Selecting  the  Gears.  The  rule  for  finding  the  gears  to  be  used 
on  the  spindle  and  lead-screw  is:  Multiply  the  number  of  threads 
on  the  lead-screw  and  the  number  of  threads  to  be  cut,  by  the  same 
number;  the  products  will  equal  the  numbers  of  teeth  on  the  gears 
to  be  used. 

Suppose  the  lead-screw  has  four  threads  per  inch,  and  ten 
threads  per  inch  are  to  be  cut.  Multiply  both  numbers  by  any 
convenient  number,  such  as  6.  Then  the  gears  should  have  24 
teeth  and  60  teeth. 

Let  a  =  Number  of  threads  per  inch  on  the  lead-screw 
b  =  Number  of  threads  per  inch  to  be  cut 
c  =  Any  convenient  number 

Then          a Xc  =  Number  of  teeth  of  gear  on  stud 

bXc  =  Number  of  teeth  of  gear  on  lead-screw     . 

If  the  gears  thus  found  are  not  at  hand,  multiply  by  some  other 
number.  Thus,  suppose  gears  of  60  and  24  teeth  were  not  available; 
multiply  4  and  10  by  any  other  number  that  would  give  the  number 
of  teeth  of  the  gears  at  hand. 

Another  way  to  find  the  gears  is  to  remember  that  the  number 
of  threads  to  be  cut  is  to  the  number  on  the  lead-screw  as  the  number 
of  teeth  on  the  screw  gear  is  to  the  number  of  teeth  on  the  stud 
gear. 

EXAMPLES  FOR  PRACTICE 

1.  The  lead-screw  has  a  pitch  of  J  inch.  What  is  the  ratio 
of  gears  to  be  used  to  cut  a  screw  with  9  threads  to  the  inch?  If 
one  gear  has  24  teeth,  how  many  should  the  other  have? 

(  1  .  91 

»  I        J-   •    ^ A 

Ans.  {  r.         . 
54  teeth 


104 


MACHINE  SHOP  WORK 


2.  The  lead-screw  has  a  pitch  of  J  inch.    What  is  the  ratio 
of  gears  to  be  used  to  cut  a  screw  with  16  threads  to  the  inch? 

Ans.     1 : 4 

3.  The  lead-screw  has  a  pitch  of  J  inch.     What  is  the  ratio 
of  gears  to  be  used  to  cut  a  screw  with  12  threads  to  the  inch? 

Ans.     1:4 

In  these  cases  the  actual  number  of  teeth  on  the  gears  to  be  used  is  obtained 
by  multiplying  the  ratio  by  some  common  multiple.  Thus,  in  Example  1, 
multiplying  by  10  gives  40  teeth  for  the  stud  gear,  and  90  for  the  screw  gear 


Fig.  164.     Simple  Lathe  Gearing 


Fig.  165.     Compound  Lathe  Gearing 


In  Example  2,  multiplying  by  20  gives  20  teeth  for  the  stud,  and  80  for 
the  screw  gear;  and  the  same  result  is  obtained  by  using  the  same  multiple  for 
Example  3. 

Every  screw-cutting  lathe  is  provided  with  a  set  of  change 
gears  from  which  selections  can  be  made.  In  order  to  facilitate 
the  choice  of  the  gears  to  be  used,  a  gear  table,  often  cast  in  raised 
letters  is  screwed  to  the  front  piece  of  the  headstock.  This  table 
shows  the  gears  to  be  used  for  cutting  such  threads  as  may  be  listed 
in  the  table. 

Compounding  Gears.  It  is  sometimes  necessary  to  cut  a  screw 
for  which  there  are  no  gears  which  make  a  direct  connection,  in 


MACHINE  SHOP  WORK 


105 


a  30  T 


which  case  the  simple  gearing  shown  in  Fig.  164  cannot  be  used. 
This  necessitates  the  compounding  of  the  gears  on  the  intermediate 
spindle  as  shown  in  the  set-up,  Fig.  165.  The  stud  is  represented 
by  A  and  the  screw  by  B.  Suppose,  with  a  lead-screw  having 
three  threads  to  the  inch,  it  is  desired  to  cut  a  screw  having  thirteen 
threads  to  the  inch.  This  makes  the  ratio  of  teeth  on  the  spindle 
gear  to  those  on  the  screw 
as  3  to  13.  The  work  can 
be  done  with  spindle  gears 
having  15,  30,  or  45  teeth, 
with  screw  gears  having  65, 
130,  and  195  teeth,  respec- 
tively. If  it  is  found  that 
there  are  no  gears  having 
15,  45,  130,  or  195  teeth  on 
hand,  compounding  must  be 
resorted  to.  To  determine 
the  gears  to  be  used,  it  must 
be  remembered  that  the 
product  of  the  numbers  of 
teeth  of  the  driving  gears 
must  be  to  the  product  of  the 
numbers  of  teeth  of  the  driven 
gears,  as  the  number  of 
threads  per  inch  on  the  lead-  Fie- 166-  change-Gear  Set-up 

screw  is    to  the  number  to 

be  cut.  In  this  case  it  is  as  3  to  13.  Multiply  each  of  these  figures 
by  any  convenient  multiple.  In  the  example  in  hand,  let  the  mul- 
tiple be  200.  Then, 

3X200      3X2X2X2X5X5 


?£>' 


13X200     13X2X2X2X5X5 

Select  from  the  factors  thus  obtained  two  sets,  each  of  which,  when 
multiplied  together,  will  give  products  equal  to  the  number  of  teeth 
that  are  on  hand. 

Thus,  in  the  numerator,  we  may  take  3X2X5,  and  2X2X5, 
giving  30  and  20  as  gears  that  are  to  be  used  as  the  spindle  and 
intermediate  drivers,  respectively. 


106  MACHINE  SHOP  WORK 

For  the  denominator,  take  13X5,  and  2X2X5X2,  or  65  and 
40,  for  the  driven  gears  of  the  intermediate  stud  and  the  screw, 
respectively.  Placing  these  in  position  as  in  Fig.  166,  we  have 

Gear  A  with  30  teeth 
Gear  C  with  65  teeth 
Gear  D  with  ^0  teeth 
Gear  B  with  40  teeth 

EXAMPLE  FOR  PRACTICE 

It  is  desired  to  cut  a  screw  with  11  threads  to  the  inch  on  a 
lathe  having  a  lead-screw  with  a  pitch  of  i  inch.  The  gears  avail- 
able have  30,  40,  45,  50,  55,  60,  65,  70,  80,  90,  and  100  teeth,  respec- 
tively. What  ones  are  to  be  used,  and  where? 

f  Spindle  40  teeth 

.       I    Intermediate  driven  55  teeth 

I    Intermediate  driver  50  teeth 

I  Screw  100  teeth 

The  preceding  examples  may  be  taken  as  applying  to  either 
right-  or  left-hand  threads.  The  change  or  direction  in  the  travel 
of  the  carriage  is  obtained  by  shifting  the  handle  at  its  right  center, 
Fig.  165,  thus  reversing  the  rotation  of  the  lead-screw. 

The  following  description  of  the  method  of  cutting  a  V-thread 
will  suffice  to  illustrate  the  cutting  of  any  form,  with  the  slight 
changes  which  are  necessary  in  the  other  forms  because  of  the  shape 
of  the  tool  employed: 

First  set  the  cutting  point  so  that  a  line  at  right  angles  to  the 
lathe  axis  bisects  the  tool  angle,  and  so  that  the  tool  is  exactly  at 
the  height  of  the  center. 

The  relation  between  the  rotary  motion  of  the  work  and  the 
axial  traverse  of  the  tool,  determines  the  pitch  of  the  thread 
being  cut;  and  jthe  mechanism  connecting  the  work  and  the  tool 
must  be  of  a  positive  character. 

Owing  to  the  lost  motion  of  backlash  in  the  mechanism  con- 
necting the  tool  and  the  work,  the  tool  cannot  be  returned  to  the 
starting  point  for  a  new  and  deeper  cut  by  simply  reversing  the  lathe. 
The  tool  must  first  be  withdrawn,  the  lathe  reversed,  the  tool 
returned  to  the  starting  point,  and  then  advanced  for  the  new  cut. 


MACHINE  SHOP  WORK 


107 


To  place  the  tool  for  the  new  cut  with  accuracy,  a  stop  or  graduated 
device  is  provided. 

When  the  work  is  removed  from  the  lathe  for  testing,  care  should 
be  taken  in  replacing,  to  get  the  tail  of  the  dog  in  the  same  slot 
in  the  faceplate  that  was  used  to  cut  the  original  thread;  this  can 
be  done  by  marking  or  otherwise  indicating  the  slot. 

Hand=Chasing.  The  ordinary  methods  of  cutting  screws  have 
already  been  described.  Where  great  accuracy  is  not  necessary, 
the  threads  may  be  chased  by  hand.  A  chaser,  or  chasing  tool, 
differs  from  the  ordinary  thread-cutting  tool,  in  that  it  has  a  number 
of  cutting  points  instead  of  but  one.  When  a  chaser  is  operated 
by  a  power  feed,  it  is  customary  to  have  a  shaft  revolve  at  the  same 
rate  or  at  an  even  multiple  of  the 
rate  of  the  lathe  spindle.  This  shaft 
carries  a  master  thread  into  much 
a  section  of  a  nut  drops.  The 
handle  connected  with  the  nut  car-\ 
ries  the  chasing  tool.  WThen  the  nut 
is  in  contact,  the  tool  is  cutting. 
At  the  end  of  the  cut,  the  tool  is 
lifted  out,  and  with  it  the  nut  dis- 
engages with  the  thread. 

Hand-chasing  requires  a  great 
deal  of  skill  in  order  that  a  good 
piece  of  work  may  be  done.  The 
chasing  tool  has  a  number  of  points, 
as  shown  in  Fig.  167.  The  work  must  be  run  rapidly  in  the 
lathe.  The  tool  is  held  in  both  hands,  and  is  supported  on  a 
rest  similar  to  that  shown  for  the  hand-turning  tools  in  Fig.  90. 
The  first  left-hand  tooth  of  the  chaser  is  brought  lightly  against 
the  right-hand  edge  of  the  work.  The  handle  is  given  a  quick  twist 
from  left  to  right,  throwing  the  teeth  in  the  opposite  direction. 
It  is  well,  after  the  first  twist,  to  stop  the  lathe  and  examine  the 
work.  If  the  operation  has  been  properly  performed,  the  second 
tooth  will  be  found  to  have  entered  the  groove  made  by  the  first. 
A  short  length  of  thread  will  have  been  cut  out,  the  pitch  being  the 
same  as  that  of  the  chaser.  If  this  is  correct,  the  lathe  may  again 
be  started  and  the  chaser  applied  as  before.  On  the  second  trial 


Fig.  167.     Hand  Chaser  Cutting 
Outside  Thread 


108 


MACHINE  SHOP  WORK 


Fig.  168.     Hand  Chaser  Cutting  Inside  Thread 


the  thread  may  be  run  to  its  full  length.     The  finishing  of  the  thread 
is  done  by  merely  repeating  the  operation.     A  fine  cut  is  taken  with 

each  application  of  the  chaser 
for  the  whole  length  of  the 
thread,  until  the  full  depth 
has  been  cut.  In  doing  this 
work,  the  rear  or  right-hand 
side  of  the  chaser  should  be 
pressed  more  firmly  against 
the  piece  being  cut  than  the 
front,  because  the  threads  with 
which  that  portion  of  the  tool 
is  engaged  are  more  deeply 
cut  than  at  the  front.  In 
addition  to  cutting,  these  teeth  also  guide  those  in  front.  The 
reason  for  running  the  lathe  at  a  high  rate  of  speed,  is  that  the 
movement  of  the  chaser  is  less  likely  to  be  checked  or  thrown  aside 
by  seams  or  inequalities  in  the  density  of 
the  metal  than  it  would  be  if  the  lathe 
were  to  run  slowly.  Inside  threading  may 
be  done  by  means  of  the  inside  chaser  shown 
in  Fig.  168. 

Drilling  in  the  Lathe.  The  lathe  can 
also  be  used  for  drilling.  When  such  work 
is  to  be  done,  the  drill  may  be  held  in  the 
spindle,  and  the  work  forced  up  against  it 
by  the  screw  of  the  tailstock;  or  the  work 
may  be  revolved,  and  the  drill  forced  in  by 
the  tailstock  screw.  When  the  first  method 
is  followed,  the  drill  may  be  put  into  a 
socket  prepared  for  it  in  the  spindle  of  the 
lathe,  or  the  drill  may  be  held  by  a  drill 
chuck,  as  shown  in  Fig.  169.  This  chuck 
may  be  used  in  the  tailstock  to  hold  twist 
drills,  or  to  hold  flat  drills  which  are  forged 
from  round  stock.  Flat  drills  made  from  flat  stock  are  centered 
at  the  rear  end,  and  held  against,  and  fed  forward  by,  the  dead 
center.  In  this  case,  a  slotted  rest  held  in  the  tool-post,  as  in 


Fig.  169.     Drill  Held  by 
Drill  Chuck 


MACHINE  SHOP  WORK 


109 


Fig.  64,  Part  I,  prevents  the  drill  from  turning,  and  aids  in  starting 
the  drill  true. 

When  the  drill  is  held  in  the  headstock,  the  work  may  be  fastened 
to  the  carriage  and  fed  against  the  drill,  or  it  may  be  held  by  means 
of  a  suitable  device  used  in  the  tailstock.  For  this  purpose  the  drill 


Fig.  170.     Drill  Pad  for  Flat  Work 


Fig.  171.     Drill  Pad  with  V-Center  for  Holding  Round  Stock 


pad,  shown  in  Fig.  170,  may  be  used,  especially  if  the  work  is  flat. 

The  V-center,  shown  in  Fig.  171,  is  used  when  it  is  desired  to  drill 

through  the  axis  of  a  piece  of  round  stock. 

The  shape  of  the  groove  prevents  the  work 

from  turning;  and  the  angle,  being  always  in 

the  axis  of  the  lathe,  determines  accurately  the 

location  of  the  hole. 

DRILLERS 

Drilling  Operation.  Where  holes  are  to 
be  cut  through  metal  using  a  rotating  tool  with 
the  cutting  edges  at  its  point,  the  operation  is 
known  as  drilling  and  the  cutting  tools  are 
termed  drills.  These  tools  may  be  of  the 
simplest  type,  as  for  example,  Fig.  172,  or 
they  may  be  of  the  more  elaborate  type  shown  in  Fig.  173,  known 


Fig.  172.     Flat  Drill  of 
Simplest  Type 


110 


MACHINE  SHOP  WORK 


as  a  twist  drill.  While  it  is  evident  that  any  machine  having  a  rotat- 
ing spindle  may  be  used  to  drill  holes,  it  is  more  usual  to  do  this 
in  a  machine  designed  especially  for  and  equipped  to  do  this  work. 
Drilling  machines  of  the  horizontal  type  are  sometimes  made, 
but  the  more  common  type  is  known  as  the  vertical  drilling 


Fig.  173.     Typical  Tapered  Shank  Twist  Drill 


Fig.  174.     Sensitive  Driller 
Courtesy  of  Washburn  Shops,  Worcester, 
Massachusetts 


machine,  often  called  a  drill 
press.  These  have  1,  2,  3,  or 
more  spindles  in  a  great  variety 
of  sizes,  weights,  and  designs, 
many  of  which  are  made  for 
purposes  of  special  drilling  only. 
The  ones  shown  will  be  those  of 
the  kind  commonly  found  in  the 
ordinary  machine  shop 

While  it  is  common  practice 
to  designate  both  the  drilling 
machine  and  the  cutting  tool  as 
drills,  for  convenience  of  descrip- 
tion in  the  accompanying  text, 
the  machine  will  be  termed  a 
driller  and  the  cutting  tool  as  a 
drill.  It  may  also  be  said  that 
this  practice  is  meeting  with 
general  favor. 

Sensitive  Driller.  InFig.174 
is  shown  a  drilling  machine  de- 
signed for  use  with  the  smaller 
sizes  of  drills  on  work  under 
conditions  which  render  it  nec- 
essary to  "feel"  what  the  cut- 
ting lips  are  doing.  It  will  be 
noticed  that  there  are  no  trains 
of  gearing  present  in  the  spindle 
driving  mechanisms  and  that  the 


MACHINE  SHOP  WORK  111 

tool  is  pressed  or  fed  into  the  work  by  using  the  simplest  and  most 
direct  device  possible,  a  lever,  a  pinion  and  shaft,  and  a  rack  which 
engages  the  pinion.  This  is  the  simplest  form  of  effective  drilling 
machines  and  is  known  as  a  sensitive  driller.  In  the  cut,  Fig.  174, 
B  is  the  base,  P  the  post,  T  the  table,  S  the  spindle,  H  the  head 
bracket,  C  back-cone  pulley,  I  the  idler  pulleys,  A  the  spindle  pulley, 
and  L  the  hand  or  feed  lever.  It  will  be  noted  that  the  construction 
permits  the  upper  or  square  table  to  be  swung  out  of  position, 
allowing  the  lower  or  round  table  bracket  to  be  put  into  a  position 
for  using  this  extra  table  and  the  crotch  and  cup  centers.  The 
nose  of  the  spindle  is  bored  out  at  its  axis  to  what  is  known  as  a 
No.  1  Morse  taper.  Drills  fitted  with .  this  taper  can  be  used 
direct,  or  straight  shank  drills  may  be  used  in  a  drill  chuck  having 
a  standard  No.  1  Morse  taper  stem  or  shank  to  fit  the  spindle. 

Power  Feed  Driller.  The  heavier  types  of  these  machines  are 
usually  provided  with  back  gearing  similar  to  that  employed  in 
engine  lathes.  The  power  feed  is  obtained  by  suitable  spindles 
and  trains  of  gearing  which  drive  the  rack  and  sleeve  by  using  a 
pinion,  as  in  the  hand  feed  machine. 

The  essential  differences  between  this  machine  and  the  smaller 
type  are:  (a)  its  heavy  rigid  frame  and  moving  parts;  (b)  its  range 
of  spindle  speed  changes  made  possible  by  the  cones  and  back  gears; 
(c)  its  spindle  feed  by  power  gearing  instead  of  a  hand  lever;  (d)  its 
greater  spindle  driving  power  gained  largely  by  use  made  of  the  back 
gears;  and  (e)  its  sub-base  for  holding  the  heavier  work. 

While  the  machine  shown  in  Fig.  175  is  belt  driven,  as  relates 
to  its  stepped  cone  pulleys,  the  work  spindle  S  is  gear  driven  and 
gear  fed.  The  trains  of  gearing,  which  rotate  the  spindle  and  which 
provide  for  feeding  it  downward,  are,  as  in  all  modern  geared 
machines,  so  covered  as  not  to  be  plainly  visible.  The  back  gears 
are  engaged  at  all  times,  but  are  brought  into  active  driving  service 
by  operating  a  clutch  B  through  use  of  the  clutch  lever  C.  The 
smaller  spindle  A  passes  downward  through  a  cone  of  gears  located 
in  the  gear  box  G  to  a  train  of  gearing  which  is  mounted  upon  the 
head  bracket.  The  head  bracket  carries  not  only  the  work  spindle 
sleeve  and  feed  rack,  but,  besides  these,  has  mounted  on  its  frame 
the  power  and  the  hand  feed  mechanisms.  The  hand  feed  is  oper- 
ated by  rotating  the  hand  wheel  H.  The  power  feed  is  controlled 


112 


MACHINE  SHOP  WORK 


Fig.  175.     Standard  Power  Feed  Driller 
Courtesy  of  Reed-Prentice  Company,  Worcester,  Massachusetts 

by  the  clutch  lever  L.  The  changes  of  feed  from  fine  to  coarse  are 
made  by  means  of  a  slip  key  actuating  the  cone  feed  gears  through 
the  shaft  E  and  the  smaller  hand  wheel  F. 


MACHINE  SHOP  WORK 


113 


Multiple  Spindles.  Drilling  machinery,  both  horizontal  and 
vertical,  is  sometimes  provided  with  more  than  one  spindle.  IE 
the  smaller  drillers  of  the  vertical  type,  the  spindles  are  fixed  in  theii 
relative  positions,  and  are  not  intended  to  be  operated  simul- 
taneously, the  work  passing  from  one  spindle  to  another.  The  true 


Fig.   176.     Typical  Multi-Spindle  Driller 

multi-spindle  driller,  Fig.  176,  is  for  the  purpose  of  drilling  several 
.holes  at  one  time  and  in  any  relative  position  within  the  limits  of 
adjustment  of  the  machine. 

Radial  Driller.  Another  form  of  driller,  known  as  the  radial, 
is  being  extensively  used.  It  is  shown  in  Fig.  177.  The  drill  spindle 
is  carried  on  the  horizontal  arm,  and  is  arranged  to  be  set  and 


114 


MACHINE  SHOP  WORK 


run  at  any  position  on  this  arm.  At  the  same  time,  the  arm  may 
be  swung  around  and  clamped  in  any  vertical  or  horizontal  position 
about  the  upright.  These  drillers  are  usually  employed  on  heavy 
work  where  several  holes,  differently  positioned,  are  to  be  drilled. 

In  the  case  of  the  driller  shown  in  Fig.  175,  the  work  is  usually 
light,  and  can  be  readily  shifted  so  that  the  position  of  the  holes 
can  be  brought  beneath  the  drill.  In  heavy  work  such  as  machine 


Fig.  177.     Radial  Driller  with  Four-Foot  Arm  for  Heavy  Duty 
Courtesy  of  Reed-Prentice  Company,  Worcester,  Massachusetts 

frames,  however,  this  cannot  be  done.  It  is  therefore  necessary 
to  be  able  to  shift  the  drill  and  place  it  in  a  position  to  do  the  work. 
The  radial  driller  affords  the  means  of  doing  this. 

Universal  Radial.  Where  the  vertical  spindle  carrying  the 
drill  can  be  rotated  in  the  vertical  plane,  holes  cannot  only  be  drilled 
in  any  position,  but  also  at  any  angle.  Such  a  driller  is  called  a 
universal  radial. 


MACHINE  SHOP  WORK 


115 


Laying  Out.  The  position  of  the  holes  is  usually  laid  out  for 
the  guidance  of  the  man  at  the  driller.  The  work  is  best  done  as 
shown  in  Fig.  178.  The  center  punch  mark,  indicated  by  A, 
shows  the  location  of  the  center  hole.  The  circle  upon  which  the 
prickpunch  marks  BBBB  are  placed,  gives  the  location  of  the 
circumference  of  the  hole.  To  drill  the  hole,  place  the  point  of 
the  drill  in  the  center  punch  mark  Ay  and  drill  into  the  metal 
until  the  center  punch  mark  has  been  slightly  enlarged,  as  shown 
by  the  circle  C.  Then  raise  the  drill  and  examine  the  work. 
If  the  countersink,  or  hole  whose  circumference  is  indicated  by  the 


Fig.  178.    Layout  for 
Drilling  Hole 


Fig.  179.    Chiseling 

Countersink  when 

not  Concentric 


Fig.  180.  Action  of  Groove 

in  Making  Drill  Hole 

Concentric 


circle  (7,  is  exactly  concentric  with  the  outer  circle  BBBB,  then 
the  drill  may  be  put  down  and  the  hole  drilled. 

Owing,  however,  to  various  causes,  it  is  not  often  that  the 
circle  will  be  concentric.  This  may  be  caused  by  one  of  three 
conditions,  an  uneven  grinding  of  the  drill;  a  distortion  of  the  metal 
by  the  center  punch;  or  an  eccentric  motion  of  the  drill  point,  due 
to  a  lack  of  trueness  in  the  running  of  the  spindle. 

When  the  countersink  is  not  concentric,  the  drill  must  be  drawn 
back  to  the  central  position.  The  method  employed  is  shown 
in  Fig.  179.  A  round-nosed  chisel  is  used  to  cut  a  groove  E  down 
the  side  of  the  countersink,  on  the  side  that  is  farthest  from  the 
circle  BBBB.  The  depth  of  this  groove  depends  upon  the  amount 
of  eccentricity  of  the  countersink  and  the  depth  to  which  it  has 
been  drilled.  The  drill  is  then  run  down  again  and  the  groove 
drilled  out.  The  action  of  this  groove  is  as  follows;  as  the  drill 


116 


MACHINE  SHOP  WORK 


turns,  one  cutting  edge  is  supported,  and  is  working  into  the  face 
C,  Fig.  180.  At  the  same  time,  the  cutting  edge  is  opposite  the  groove 
E.  The  drill,  therefore,  springs  into  the  groove,  as  shown.  The 
lip  then  catches  on  the  edge  of  the  groove  and  cuts  it  away,  making 
the  hole  elliptical,  and  shifting  the  center  of  the  drill  toward  its 
proper  position.  As  the  drill  sinks  deeper,  both  lips  are  in  contact 
with  the  faces  C  and  D,  and  it  has  no  further  tendency  to  shift. 
When  the  groove  has  been  drilled  out,  the  drill  must  be  again 
raised,  to  ascertain  whether  or  not  the  countersink  is  concentric 
with  the  outer  circle  BBBB.  If  not,  another  groove  must  be  cut, 
and  the  process  repeated  until  the  drill  is  correctly  positioned, 
when  the  hole  may  be  drilled.  The  prickpunch  marks  BBBB  are 

put  on  the  outer  circle  in 
order  to  indicate  its  position 
in  case  of  the  obliteration  of 
the  line  itself. 

A  twist  drill  will  usually 
clear  its  hole  of  chips.  For 
deep  holes,  this  may  not  al- 
ways occur.  It  is  then  nec- 
essary to  withdraw  the  drill 
and  clean  out  the  hole.  This 
can  be  done  by  a  piece  of 
wire  bent  at  the  end;  also  by 
using  a  blowpipe  made  of  a 
small  tube,  and  bent  to  enter 
the  hole,  so  that  the  chips  will  not  blow  up  into  the  operator's  face. 
Holes  in  cast  iron  are  more  likely  to  need  cleaning  than  holes  in 
wrought  iron  or  steel.  Where  flat  drills  are  used,  it  is  always  nec- 
essary to  clean  the  holes  at  frequent  intervals,  as  such  drills  have 
no  tendency  to  raise  the  chips  and  clear  the  holes. 

Holding  the  Work.  A  matter  to  receive  due  consideration  is 
that  the  work  must  be  held  rigidly  on  the  work  table  while  being 
drilled.  This  may  be  done  in  two  ways.  If  the  holes  are  to  be 
drilled  with  great  accuracy,  the  work  must  be  clamped  to  the  table. 
This  is  often  done  by  means  of  straps,  as  shown  in  Fig.  181.  In 
thl*  figure,  a  gland  A  is  shown  clamped  to  the  table  by  the  straps 
BB.  One  end  of  the  strap  rests  upon  the  flange  of  the  gland  and  the 


Fig.  181.     Work  Clamped  to  Table  by  Straps  for 
Accurate  Hole-Drilling 


MACHINE  SHOP  WORK 


117 


other  upon  any  convenient  piece  of  metal  C,  of  the  proper  thickness. 
The  bolt  D  is  put  up  through  a  hole  in  the  table  as  close  to  the 
work  as  possible.  WThen  the  nuts  are  screwed  down,  they  then  put 
the  greatest  available  pressure  on  the  work,  and  hold  it  fast.  The 
strap  B  is  made  of  flat  iron.  It  has  one  or  more  holes  drilled  in  it 
to  permit  the  passage  of  bolts. 

Another  method  of  holding  work  in  the  drill  press  is  by  means 
of  a  post.  This  is  shown  in  Fig.  182.  It  consists  of  a  post  A,  set 
loosely  in  one  of  the  holes  in  the  table.  As  the  drill  is  forced  against 
the  work,  it  tends  to  turn  the  latter  with  it.  When  the  work  strikes 
the  post,  it  is  stopped  and  held  while  the  hole  is  drilled.  This  will 
not  hold  the  work  -perfectly  steady.  It  allows  the  latter  to  move 
with  the  eccentricity  of 
the  motion  of  the  drill, 
but  it  is  in  very  common 
use  where  extreme  accu- 
racy is  not  essential,  ^or 
example,  where  a  finished 
bolt  is  to  be  used  with 
a  driving  fit,  the  work 
must  be  securely  fas- 
tened so  that  the  diam- 
eter of  the  hole  may  be 
true.  Where  a  machine 
bolt  made  of  rough  iron 
is  to  be  used,  the  hole  is  drilled  y^  inch  larger  than  the  nominal  size 
of  the  bolt.  Here  accuracy  is  not  even  attempted;  a  variation  of 
•£2  inch  in  the  diameter  of  the  hole  is  of  no  account.  Therefore,  in 
such  cases,  the  work  may  be  allowed  merely  to  rest  against  the  post. 

This  question  of  holding  the  work  does  not  apply  to  drills  of  the 
multi-spindle  class,  Fig.  176.  Evidently  the  tendency  of  one  drill  to 
rotate  the  work  is  counteracted  by  the  action  of  another  drill. 

An  angle  iron  forming  a  right  angle  with  the  work  table,  is 
used  in  many  cases  to  support  the  work  where  the  hole  cannot  be 
properly  located  by  the  use  of  the  table  alone.  The  clamping  of 
the  work  to  the  angle  iron  must  be  very  rigid  to  resist  the  pressure 
of  the  drill.  A  tilting  table  is  sometimes  used,  so  that  the  holes 
may  be  drilled  at  any  required  angle.  At  least  one  manufacturer 


Fig.  182.     Use  of  Table  Stud  for  Drilling 


118  MACHINE  SHOP  WORK 

is  putting  on  the  market  a  horizontal  drilling  machine  which  can 
drill  five  sides  of  a  cube  at  any  angle,  with  but  one  setting  of  the  work. 
Tapping.  Drilling  machines  may  also  be  used  for  tapping. 
This  requires  a  reversing  device  for  backing  out  the  tap.  The  back- 
ing-out is  done  at  a  much  higher  speed  than  the  tapping.  The  tap 
is  held  in  a  friction  head  that  will  slip  when  the  tap  strikes  the 
bottom  of  the  hole.  The  use  of  collapsing  taps,  especially  on 
diameters  of  one  inch  and  over,  renders  the  backing-out  unneces- 
sary, and  quickens  the  operation.  Studs  may  be  set  by  the  same 
device,  so  that  cylinder  flanges  may  be  drilled,  tapped,  and  the  studs 
set,  without  removing  the  work  from  the  machine.  Duplicate 
drilling  by  means  of  jigs  will  be  considered  later.  • 

PLANERS 

As  the  name  indicates,  the  planer  is  used  for  finishing  flat 
surfaces.  In  the  ordinary  planer,  the  work  is  moved,  and  the  tool 
is  at  rest.  A  common  form  of  this  tool  is  shown  in  Fig.  183.  It 
consists  of  a  bed  A,  upon  the  upper  surface  of  which  suitable  guides 
or  ways  are  planed.  The  platen  B  is  made  to  travel  back  and  forth 
upon  these  ways.  The  platen  has  a  rack  on  its  under  surface,  into 
which  the  gear  C  meshes.  This  gear  is  driven  by  a  train  of  gears 
from  the  shaft  carrying  the  pulley  D.  The  tool  is  carried  on  the 
tool-head  E,  where  it  can  be  given  a  slight  vertical  motion  or  feed. 
This  tool-head  may  be  fed  across  the  machine  by  the  screw  i,n  the 
cross-rail  F.  The  latter  may  be  raised  and  lowered  by  the  shaft 
and  gearing  shown  at  the  top.  This  gearing  turns  two  vertical 
screws  running  in  nuts  attached  to  the  cross-rail. 

The  reciprocating  motion  of  the  planer  table  is  obtained  as 
follows :  The  pulleys  D  and  G  run  loose  on  the  shaft,  and  are  driven 
in  opposite  directions  by  belts  from  an  overhead  countershaft.  The 
center  pulley  is  fixed  to  the  shaft,  and  either  belt  may  be  moved  over 
on  this  pulley  by  the  belt-shifters  J,  which  are  moved  in  opposite 
directions  by  a  connection  with  the  shifting  lever  7,  connected  with 
them  by  suitable  mechanism  inside  the  bed,  and  acted  upon  by  the 
reversing  dogs  H  H,  which  are  adapted  to  be  adjusted  at  any  point 
in  the  length  of  the  table,  according  to  the  position  of  the  work  and 
the  length  of  the  stroke  desired. 


MACHINE  SHOP  WORK 


119 


The  planer  shown  in  Fig.  183  has  but  one  head  for  holding  a 
tool.  In  large  planers  it  is  customary  to  have  two  heads  on  the 
cross-rail,  so  that  two  tools  may  be  cutting  simultaneously,  thus 
doubling  the  capacity  of  the  machine.  The  vertical  feed  of  the  tool 
is  also  operated  automatically;  and  in  a  planer  having  two  heads, 
both  vertical  and  lateral  feeds  are  independent  of  each  other. 


133.     Common  Type  of  Planer 


Fig.  184  shows  a  large  planer  equipped  with  two  heads  on  the 
cross-rail,  and  a  still  further  equipment  of  two  heads  with  automatic 
vertical  feeds  on  the  side  posts.  Thus  arranged,  the  machine  is 
capable  of  handling  very  large  work,  and  of  keeping  four  tools 
cutting  simultaneously.  The  table-operating  mechanism  within  the 
bed  is  substantially  the  same  in  nearly  all  except  some  special  planers. 
In  this  planer,  there  is  a  driving  belt  on  each  side  of  the  machine, 
one  running  the  table  forward,  and  the  other  backward,  the  rod 
carrying  the  belt-shifters  passing  entirely  through  the  machine, 


120 


MACHINE  SHOP  WORK 


MACHINE  SHOP  WORK 


121 


The  speed  of  travel  forward  of  the  table  is  the  ordinary  cutting 
speed;  while,  to  save  time,  the  return  or  backward  movement  is  as 
fast  as  the  driving  mechanism  will  permit.  The  ratio  of  forward 
to  backward  speeds  will  be  from  2  to  1  (in  very  large  planers),  to  4 
to  1  (in  small  planers). 

Ordinarily  the  tool  cuts  only  when  the  platen  is  moving  toward 
the  right,  Fig.  183.  As  a  result  of  this  condition,  the  platen  is 
made  to  move  more  rapidly  toward  the  left  than  toward  the  right. 
This  is  accomplished  by  varying  the  speeds  of  the  pulleys  D  and  G. 
The  usual  ratio  of  the  speeds  of  these  pulleys  is  2  to  1  or  3  to  1. 

The  feed  of  the  tool  is  accomplished  by  a  friction  clutch  driving 
the  vertical  rack  K.  This  acts  only  at  a  point  near  the  end  of  the 
travel  of  the  platen.  It  is  so  arranged  that  any  reasonable  vertical 
or  horizontal  feed  may  be 
given  to  the  tool. 

The  machine  is  driven 
by  three  driving  pulleys 
placed  side  by  side  on  the 
same  shaft,  the  central 
one  of  the  three  being 
keyed  to  the  shaft.  The 
reversal  of  the  motion  of 
the  platen  is  obtained  by 
shifting  one  or  the  other  of  the  belts  onto  the  central  pulley. 

Planer  Tools.  The  tools  used  with  planers  do  not  differ  essen- 
tially from  those  described  for  lathe  work.  The  same  rules  apply 
regarding  the  holding  of  the  tool.  It  should  project  as  short  a  dis- 
tance as  possible  beyond  the  point  of  support.  When  there  is  an 
jexcessive  projection,  care  should  be  taken  that  the  tool  is  so  set 
that  it  will  not  spring  into  the  work.  On  the  lathe  this  can  be 
prevented  by  setting  the  point  of  the  tool  on  a  line  with  the  center. 
In  Fig.  185  the  tool  tends  to  spring  and  turn  about  the  point  A  as 
a  center.  The  dotted  line  at  the  point  shows  how  this  tends  to  throw 
it  into  the  work.  The  same  thing  is  shown  in  the  planer  tool  in 
Fig.  186.  This  tendency  can  be  overcome  by  forging  the  tool  so 
that  the  cutting  point  is  behind  a  perpendicular  from  the  point  of 
support,  as  shown  by  the  dotted  lines  in  Fig.  186.  In  the  latter 
case,  the  spring  of  the  tool  tends  to  take  it  out  of  the  work. 


Fig.  185.     Lathe  Tool  Improperly  Set  Up 


122 


MACHINE  SHOP  WORK 


B. 


Holding  the  Work.  The  work  is  usually  held  on  the  planer  by 
clamping  it  down  with  straps  in  a  manner  similar  to  that  shown 
in  Fig.  181.  Where  the  whole  upper  surface  is  to  be  planed  over, 

, -,  holes  are  sometimes  drilled  in  the 

sides,  into  which  the  rounded  ends 
of  straps  are  set. 

Fig.  187  shows  the  manner  of 
clamping  down  a  machine  bed  A, 
by  the  use  of  straps  BB  having 
the  ends  bent  downward  so  as  to 
avoid  the  use  of  the  loose  blocks  C 
as  shown  in  Fig.  181.  In  addition 
to  the  straps,  there  must  be  plugs 
C  placed  in  the  circular  holes  in 
the  planer  table,  which  take  the 
thrust  due  to  the  action  of  the 
cutting  tool,  and  prevent  the  bed 
A  from  moving  on  the  table.  In 
planing  the  pedestal  Z),  it  will  be 
necessary  to  provide  still  further  support,  which  is  done  by  the 
brace  E,  placed  against  the  plug  F,  and  adjusted  to  the  proper 
length  by  the  screw  and  check-nut  at  e. 

It  is  impossible  to  give  more  than  general  directions  for  clamping 
work  on  a  planer.  A  great  variety  of  blocking,  'clamps,  and  bolts 


Fig.  186.     Incorrect  and  Correct  Setting 
for  Planer  Tool 


Fig.  187.     Method  of  Clamping  Down  Planing  Machine  Bed  and  Supporting  Work 

may  be  used,  such  attachments  being  suited  to  the  work  in  hand. 
It  should  be  sufficient  to  say  that  the  work  must  be  carefully  set, 
strongly  clamped  and  braced  to  prevent  movement  by  the  tool; 
and  the  clamping  should  not  distort  the  work.  As  all  castings 


MACHINE  SHOP  WORK 


123 


and  forgings  change  their  shape  when  the  surface  is  removed,  it  is 
considered  good  practice  to  release  the  clamps  before  the  finishing 


Fig.  188.     Angle  Irons  or  Knees 


Fig.  189.     Planer  Chuck  for  Holding  Work 


Fig.  190.    Planer  Centers 


cut,  in  order  that  the  piece  may  assume  its  final  shape,  and  their 
reclamp  it  without  distortion. 


124 


MACHINE  SHOP  WORK 


Angle  irons  or  knees,  as  shown  in  Fig.  188,  may  be  considered 
as  an  auxiliary  table  with  a  surface  at  right  angles  to  the  main  table. 
Many  useful  applications  of  these  holding  devices  will  suggest 
themselves. 


It 


Another  method  of  holding  work  is  by  using  a  planer  chuck, 
such  as  is  shown  in  Fig.  189.  In  use  the  chuck  is  bolted  to  the  platen, 
and  the  work  is  held  between  the  chuck  jaws. 

Planer  centers,  as  illustrated  in  Fig.  190,  are  very  useful  in 
machining  parts  where  accurate  circular  spacing  is  desired,  or  where 
projecting  lugs  prevent  the  work  surface  turning  in  a  lathe. 


MACHINE  SHOP  WORK 


125 


Plate  Planer.  A  special  form  of  planer  extensively  used  in 
boiler  shops  and  shipyards  is  the  plate  planer,  Fig.  191.  It  is  used 
for  planing  the  edges  of  long  plates.  The  plate  is  securely  fastened 
between  the  12  pneumatic  jacks  and  the  bed.  The  tool  is  held  in 
the  carriage  seen  in  the  center,  which  is  moved  to  and  fro  by  the 
screw,  which  in  turn  is  driven  by  the  electric  motor  through  the 
gearing  at  the  left.  For  starting,  stopping,  and  reversing  the  direc- 


GSM 


Fig.  192.     Typical  Pillar  Shaper 

tion  of  the  carriage,  a  shifting  rod  is  arranged  along  the  front  of  the 
machine,  as  shown  in  the  illustration;  handles  may  be  moved  to 
positions  of  convenience  for  the  operator  while  working  on  plates  of 
various  lengths.  The  tool  holder  is  so  arranged  that  by  the  use  of 
one  tool,  a  beveled  or  a  straight  cut  may  be  taken  in  either  direction. 
On  the  saddle  is  carried  a  platform  from  which  the  operator  may 
have  a  constant  view  of  the  tool. 


126 


MACHINE  SHOP  WORK 
SHARERS 


For  the  lighter  jobs  of  planing,  the  shaper,  or  shaping  planer, 
Fig.  1 92,  is  extensively  used.  It  possesses  the  advantage  of  rapidity  of 
action.  In  this  machine,  as  in  the  plate  planer,  the  tool  reciprocates 
while  the  work  is  at  rest.  A  suitable  mechanism  causes  the  ram 
A  to  move  to  and  fro.  When  moving  toward  the  left,  the  tool  is 


Fig.  103.     Traverse  Shaper 

cutting.  As  in  the  ordinary  planer,  the  speed  of  the  cutting  stroke 
is  less  than  the  return. 

The  piece  is  held  on  the  work  table  B,  which  may  be  adjusted 
to  any  convenient  height  suited  to  the  work  being  done.  The  tool 
is  also  allowed  a  limited  vertical  adjustment  in  the  slide  by  turn- 
ing the  handle  C.  This  is  the  ordinary  method  of  obtaining  the 
vertical  feed. 

The  horizontal  feed  is  obtained  by  moving  the  table  B  sidewise. 
In  some  shapers  it  can  be  moved  vertically  to  feed  to  or  from  the 
tool;  in  other  machines  the  horizontal  feed  is  obtained  by  causing 
the  tool  with  the  reciprocating  parts  to  move  sidewise. 


MACHINE  SHOP  WORK 


127 


The  style  of  machine  shown  in  Fig.  192,  is  called  the  pillar 
shaper;  but  where  the  tool  and  ram  move  sidewise,  it  is  called  the 
traverse  shaper,  Fig.  193.  The  character  of  the  work  done 


Fig.  194.     Vertical  Blotter 


on  the  shaper  is  the  same  as  that  done  on  the  planer;  but  as  a  rule 
the  shaper  is  used  for  the  smaller  and  more  delicate  parts  which 
could  not  be  handled  quickly  on  the  planer.  The  shaper  has  the 
additional  advantage  of  a  change  of  speed,  which  allows  small 


128 


MACHINE  SHOP  WORK 


Fig.  195.      Bar 

for  Slotting 

Locomotive 

Trains 


Fig.  196. 

Slotting  Tool 

for  Cutting 

Keyways 


Fig.  197. 

Slotting  Tool 

with  Large 

Rake 


pieces,  especially  of  the  softer  metals,  to  be  machined 
at  a  maximum  rate. 

Slotter.  Another  machine  tool  which  is  not  used 
as  commonly  as  its  many  good  qualities  would  seem 
to  warrant,  is  the  slotter,  Fig.  194.  It  is  in  reality  a 
shaper  with  the  tool  reciprocating  vertically  instead 
of  horizontally.  It  is  used  for  working  on  heavy 
pieces,  and  especially  in  places  where  an  irregular 
contour  is  to  be  formed.  The  thrust  on  the  tool  is 
vertical,  and  it  and  the  machine  must  be  very  stiff. 
The  work  done  frequently  partakes  of  the  nature  of 
forming  the  inside  of  a  hole  where  the  tool  must 
project  the  whole  length  of  the  cut  below  the  bottom 
of  the  head.  Such  a  case  is  that  of  the  slotting  of 
locomotive  frames.  The  best  type  of  tool  for  such 
a  class  of  work  is  a  strong  bar,  as  shown  in  Fig.  195. 
The  bar  is  held  in  the  tool  head  just  as  any 
tool  would  be.  Near  the  lower  end,  it  carries  the  cut- 
ting tool,  which  may  be  fastened  by  a  set  screw  or 
wedge.  Such  a  tool  should  always  be  used  when  it  is 
possible.  It  has  the  advantage  of  being  stiffer  and 
less  likely  to  spring  than  a  common  forged  tool. 

The  tool  used  in  a  slotting  machine  differs  from 
that  used  in  the  lathe  or  planer,  in  that  the  direction 
of  the  cutting  motion  is  different.  Fig.  196  illustrates 
a  slotting  tool  used  for  doing  such  work  as  the  cut- 
ting of  keyways  in  the  hubs  of  pulleys.  It  will  be 
seen  that  if  the  tool  is  moved  in  the  direction  of  the 
arrow,  the  face  B  becomes  the  one  against  which 
the  chip  bears.  It  therefore  corresponds  to  the  top 
of  the  lathe  tool.  The  sharper  the  slope  given  to  the 
face  B,  the  keener  the  edge,  just  as  increasing  the  top 
rake  of  the  lathe  tool  increases  its  sharpness.  The 
face  A  must  also  be  cut  away  as  indicated.  This 
corresponds  to  the  clearance  of  the  lathe  or  planer 
tool.  It  is  quite  possible,  at  times,  to  give  these 
tools  a  larger  amount  of  rake.  Such  a  form  is  shown  in 
Fig.  197.  The  shape  of  these  tools  is  such  that  they  are 


MACHINE  SHOP  WORK  129 

very  strong  in  the  direction  of  the  thrust,  besides  having  a  keen 
cutting  edge. 

The  slotter  has  automatic  feeds  of  three  kinds — namely,  lateral, 
transverse,  and  circular — hence  a  considerable  variety  of  work  can 
be  done  upon  it.  The  stroke  of  the  vertical  ram  which  carries  the 
tool  can  be  made  any  length  of  cut  from  zero  to  full  stroke,  and 
its  location  with  relation  to  the  work  table  can  be  adjusted  according 
to  the  height  of  the  work  to  be  done.  Like  the  shaper,  it  has  a  quick 
return  after  the  cutting  stroke,  and  it  is  provided  with  four  changes 
of  speed.  This  renders  it  available  for  quite  a  large  range  of  work. 


HEAVY  UNIVERSAL  MILLING  MACHINE 

Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  Island 


MACHINE  SHOP  WORK 

PART  III 


POWER=DRIVEN  TOOLS— (Continued) 

MILLING  MACHINES 

Milling  Machine  vs.  Shaper  and  Planer.  The  operation  known 
as  milling  differs  so  radically  from  the  removal  of  metal  by  methods 
previously  described,  that  it  merits  much  more  careful  and  lengthy 
discussion  than  has  been  devoted  to  the  other  methods.  Owing,  also, 
to  its  increasing  importance  and  general  use,  it  calls  for  a  some- 
what detailed  discussion.  While  milling  is  coming  rapidly  into  favor 
as  a  means  of  doing  work  formerly  done  on  the  shaper  and  planer, 
it  does  not  follow  that  the  shaper  and  planer  are  to  be  entirely 
abandoned.  There  has  been  a  tendency  to  belittle  the  planer  and 
shaper  in  favor  of  the  milling  machine.  This  tendency  is  not 
altogether  warranted  even  by  the  rapid  and  economical  method  of 
milling.  There  is  a  large  class  of  wTork  which  can  be  done  as  accurately 
• — and  in  many  cases  as  cheaply — by  means  of  a  single-pointed  tool 
such  as  is  used  in  the  planer  and  shaper. 

Simple  M  illing  Operations.  The  fundamental  difference  between 
planing  and  milling  lies  in  the  character  of  the  tool  employed.  The 
planer  uses  a  fixed  single-pointed  tool,  with  a  reciprocating  motion 
either  of  the  tool  or  of  the  work.  Milling  is  performed  by  the  use 
of  a  rotating  tool  with  several  cutting  points.  This  rotary  multiple 
cutter  is  the  basis  of  all  milling  operations;  and,  as  the  saw  may  be 
taken  as  a  good  example  of  such  a  cutter,  so  the  work  done  by  the 
circular  saw  in  cutting  metal  may  be  said  to  be  an  example  of  milling, 
Fig.  198.  The  ordinary  milling  cutter  is  nothing  more  than  a  saw 
which  has  exceptionally  broad  teeth  and  in  which  the  contour  of  the 
cutting  blades  is  made  to  suit  the  work  in  hand. 

It  was  but  a  step  to  make  a  saw  wide  enough  to  cover  a  con- 
siderable surface,  or  to  have  a  thick  saw  with  a  suitably  formed 
cutting  edge.  Several  saws  of  different  shapes  and  sizes  can  be 


132 


MACHINE  SHOP  WORK 


mounted  in  a  gang  on  an  arbor,  and  perform  operations  which  it 
would  be  hard  to  duplicate  on  the  shaper  or  planer.  Even  in  the 
present  age  of  special  machines  for  milling,  a  great  deal  of  work  of 
this  character  is  still  performed  by  the  method  indicated. 


Fig.  198.     Sawing  Flat  Stock 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  Island 

One  of  the  great  advantages  of  milling  is  the  certainty  of  exact 
duplication — a  feature  of  prime  importance  in  the  manufacture  of 
interchangeable  work. 

About  the  first  machine  built  exclusively  for  milling  was  the 
so-called  Lincoln  miller,  Fig.  199,  which  consists  essentially  of  a  bed 


MACHINE  SHOP  WORK 


133 


carrying  the  equivalent  of  the  headstock  and  tailstock  of  a  lathe, 
with  means  for  rotating  the  cutter  arbor,  which  is  carried  directly 
by  the  headstock  spindle,  and  steadied  and  supported  by  the  tail- 
stock.  There  is  also  provided  a  table  upon  which  the  work  can  be 
fastened  either  directly  or  by  means  of  a  vise;  and  an  automatic  feed 


Fig.  199.     Lincoln  Milling  Machine 
Courtesy  of  Pratt  and  Whitney  Company,  Hartford,  Connecticut 

across  the  machine  at  right  angles  to,  and  below,  the  cutter  arbor. 
This  type  of  machine  in  various  designs  is  much  used  in  modern 
manufacturing. 

MILLING  CUTTERS 

Classification.  As  the  type  of  cutter  used  determines,  in  a  large 
measure,  the  design  of  the  machine  itself,  it  will  be  better  at  this 
point  to  take  up  a  description  of  some  of  the  different  cutters, 


134 


MACHINE  SHOP  WORK 


in  order  that  the  adaptation  of  the  machine  to  the  cutter  may  be 
clearly  seen. 

Cutters  are  classified  according  to  their  form  or  the  use  to  which 
they  are  put,  some  of  the  more  common  types  of  these  devices  being 
as  follows: 

Straddle  mill 

Straight  end  mill 

Spiral  end  mill 

T-slot  mill 

Formed  mill 

Inserted  blade 

Inserted-tooth  facing 

Inserted-tooth  surfacing 

Shell  mill 

Fly  or  single-tooth  cutter 

This  classification  does  not  include  any  of  the  cutters  used  in 
cutting  gears,  racks,  spirals,  helical  gears,  ratchets,  sprocket-wheels, 


1. 

Slitting 

11. 

2. 

Grooving 

12. 

3. 

Fluting 

13. 

4. 

Straight 

14. 

5. 

Angle 

15. 

6. 

Double-angle 

16. 

7. 

Straight  mill 

17. 

8. 

Spiral  mill 

18. 

9. 

Nicked-tooth  spiral  mill 

19. 

10. 

Side  mill 

20. 

Fig.  200.    Details  of  Ordinary  Milling  Cutter 

and  similar  work,  which  is  usually  considered  as  gear-cutting  work. 
However,  ratchet  teeth  may  be  cut  with  an  angle  cutter;  brass  gears, 
with  a  single-tooth  or  fly  cutter,  properly  formed;  and  some  others 
may  be  applied  to  a  variety  of  uses,  the  cutter,  in  fact,  not  infre- 
quently displaying  a  remarkable  adaptability  to  the  varying 
conditions  of  work  and  material. 


MACHINE  SHOP  WORK 


135 


Fundamental  Characteristics.  The  several  details  of  an  ordinary 
milling  cutter  are  shown  in  Fig.  200.  A  is  the  outside  diameter; 
By  the  thickness  (or  in  mills  such  as  shown  in  Fig.  201,  the  length); 
Cy  the  diameter  of 
the  hole;  Z>,  the 
width  of  keyway;  E, 
the  depth  of  keyway; 
Fy  the  pitch  of  the 
teeth;  G,  the  top  of 
the  teeth  or  land;  H, 
the  backing-off  or 
clearance,  either  on 
the  lands  or  on  the 
side  of  the  cutter; 
J,  the  depth  of  the 
teeth;  K,  the  face  of 
the  teeth;  L,  .the  relieving  recess  made  for  the  purpose  of  reducing 
the  surface  to  be  ground;  and  M,  the  hub.  The  direction  of  revolu- 
tion is  indicated  by  the  arrow. 

Cutter  Arbor.  Fig.  202  shows  the  usual  form  of  cutter  arbor, 
in  which  A  is  the  taper  shank  fitting  the  taper-reamed  hole  in  the 
milling-machine  spindle;  B  is  the  flattened  portion  or  tang  fitting  in 
the  cross-slot  and  preventing  the  arbor  from  turning;  C  is  a  nut  used 
in  withdrawing  the  arbor  from  the  hole  when  it  has  been  forced  tightly 
into  it;  D  is  a  collar  formed  upon  the  arbor,  against  which  loose 
collars  or  the  cutter  itself  are  forced  when  placed  upon  the  arbor  at 
E  and  confined  by  the  clamping  nut  F.  The  end  G  is  finished  as  a 


Fig.  201.     Milling  Cutter  with  Spiral  Teeth 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company, 
Providence,  Rhode  Island 


Fig.  202.     Ordinary  Form  of  Cutter  Arbor 

journal  or  bearing  for  an  outer  support  attached  to  or  forming  a  part 
of  the  overhanging  arm  of  the  milling  machine.  In  the  outer  end  is 
drilled  and  reamed  a  center  hole  for  a  similar  purpose. 

Fastening  Cutter  in  Arbor.  Cutters  are  prevented  from  turning 
upon  the  arbor  in  any  one  of  four  ways — namely,  first,  by  a  key 
in  the  keyway  DE,  Fig.  200;  second,  by  being  clamped  between 


136 


MACHINE  SHOP  WORK 


loose  collars  on  the  arbor;  third,  by  being  threaded  and  screwed  on 
the  arbor;  and  fourth,  when  the  cutter  is  quite  small  and  the  work 
light,  by  a  large-headed  screw,  slotted  for  the  screwdriver,  and  tapped 
into  the  end  of  the  arbor.  In  the  latter  case,  the  thread  must  be 


Fig.  203.     Screw-Slot  Cutter 


Fig.  204.     Slitting  Saw 


right-  or  left-handed,  according  to  the  direction  of  revolution,  so  that 
the  torsional  strain  of  the  work  will  tend  to  keep  the  cutter  screwed 
tightly  against  the  shoulder. 

Usually  cutters  are  made  right-handed;  that  is,  if  held  so  that 
the  side  which  goes  against  the  collar  on  the  arbor  is  toward  the  eye, 
the  cutter  should  turn  in  the  same  direction  as  the  hands  of  a  clock. 

Locating  Position  of  Cutter.  To  locate  the  cutter  in  the  proper 
position  on  the  arbor  to  suit  the  work  to  be  done,  loose  collars  of 
various  thicknesses  are  used  on  the  arbor,  placing  as  many  on  each 


Fig.  205.     Plain  Milling 
Cutter 


Fig.  206.     Spiral  Cutter  with  Nicked  Teeth  for  Heavy  Cuts 

Courtesy  of  Becker  Milling  Machine  Company, 

Hyde  Park,  Massachusetts 


side  of  the  cutter  as  are  necessary  to  fill  the  space  between  the  fixed 
collar  Z),  Fig.  202,  and  the  clamping  nut  F.  The  cutter  and  loose 
collars  must  have  smooth,  true,  and  parallel  faces;  otherwise  the 


MACHINE  SHOP  WORK 


137 


arbor  will  be  sprung  when  the  clamping  nut  is  screwed  up,  and  will 
not  run  true. 

Plain  Milling  Cutters.  Screw-slotting  cutters,  Fig.  203,  and 
slitting  saws,  Fig.  204,  are  saws  of  a  special  type.  The  true  milling 
cutter,  Fig.  205,  has  a  face  much  wider  in  proportion  to  its  diameter 
than  the  common  slitting  saw.  It  is  for  the  production  of  surfaces, 
rather  than  for  a  thin  saw  kerf  in  separating  pieces  of  metal.  These 
plain  cutters  are  made  in  a  large  number  of  diameters  and  lengths, 
and  are  all  designed  for  the  generation  of  plane  surfaces. 

Spiral  Cutters  with  Solid  or  Nicked  Teeth.  As  we  have  seen  in 
the  case  of  reamers,  heavy  cuts  can  be  taken  more  easily  when  the 


Fig.  207.     Side  Milling  Cutters  Mounted 
as  a  Heading  or  Straddle  Mill 


Fig.    208.     Interlocking    Cutter    with 

Four  Teeth  Cut  Away 

Courtesy  of  Union  Tvrist  Drill  Company, 

Athol,  Massachusetts 


chip  is  broken  up  in  small  pieces;  therefore,  in  milling  cutters  designed 
for  roughing,  it  is  customary  to  nick  the  teeth,  Fig.  206,  in  such 
a  way  that  the  stock  left  by  one  tooth  may  be  taken  out  by  the 
following  tooth.  This  makes  the  cutting  easier.  A  plain  cutter  of 
any  considerable  length,  with  teeth  formed  by  straight  grooves,  will 
not  often  make  a  smooth  surface  because  of  the  varying  pressure  of 
the  cutter  as  one  tooth  after  another  leaves  the  work.  To  avoid 
this  springing  tendency,  cutters  are  made  with  spiral  teeth,  Fig.  201, 
either  right-  or  left-hand,  so  that  there  is  practically  a  uniform  dis- 
tribution of  pressure  at  all  points  during  the  cut. 

Side  Milling  Cutters.    When  it  is  desired  to  mill  the  side  of  a 
piece,  it  is  necessary  that  there  should  be  teeth  on  the  side  of  the 


138 


MACHINE  SHOP  WORK 


cutter.    Such  cutters  are  usually  made  comparatively  narrow  and 
with  teeth  on  both  sides,  as  shown  in  Fig.  207.    These  side  milling 


Fig.  209.     Gang  Cutter 


cutters  are  often  sold  in  pairs.    When  mounted  together,  as  in 
Fig.  207,  they  are  often  used  to  mill  off  both  sides  of  a  piece  of  work, 


Fig.  210.     Forms  of  Angle  Cutters 

as,  for  example,  a  bolt-head;  and  they  are  therefore  called  heading 
or  straddle  mills. 


MACHINE  SHOP  WORK 


139 


Interlocking  Cutters.  If  two  cutters  of  the  same  diameter  are 
mounted  together,  it  is  difficult  to  mill  a  surface  which  will  not  show 
the  line  of  separation  of  the  cutters.  This  can  be  avoided  by  making 
the  ends  of  the  cutters,  where  they  come  together,  of  such  a  shape  that 
they  interlock  one  with  the  other.  This  feature  of  interlocking, 
Fig.  208,  is  especially  valuable  when  cutting  slots  which  must  be  of 
a  definite  width.  An  ordinary  cutter  will  wear  away  by  use  or  by 
grinding,  and  thus  lose  its  correct  size.  The  thickness  of  the  inter-- 
locking cutters  can  be  maintained,  however,  by  means  of  very  thin 
.  washers;  and,  owing  to  the 
interlocking  of  the  cutters, 
no  space  will  show  between 
them. 

Gang  Mills.  Cutters 
may  be  mounted  in  gangs 
of  great  variety  and  com- 
bination, a  typical  one 
being  shown  in  Fig.  209. 
These  cutters  may  be  of 
any  desired  form,  and  can 
be  made  to  produce  a 
variety  of  shapes. 

Angle  Cutters.  The 
so-called  angle  cutters, 
Fig.  210,  are  often  em- 
ployed in  the  manufacture 
of  other  milling  cutters. 

When  used  in  making  spiral  cutters,  they  must  have  an  angle  on  both 
sides,  the  customary  angles  in  such  cases  being  40  degrees,  43  degrees, 
45  degrees,  or  48  degrees  on  one  side,  and  12  degrees  on  the  other. 
The  common  single-angle  cutters  vary  from  40  degrees  to  80  degrees, 
either  right-  or  left-hand.  Double-angle  cutters,  as  shown  in  the 
center  of  the  lower  row,  Fig.  210,  can  be  had  with  either  45  degrees, 
60  degrees,  or  90  degrees  included  angle. 

Inserted=Tooth  Cutters.  Only  such  cutters  as  are  made  from 
a  single  piece  of  tool  steel  have  been  so  far  considered.  In  large 
cutters,  however,  the  cost  of  the  steel  becomes  an  important  item,  and 
there  is  the  ever-present  danger  of  losing  a  large  amount  of  labor 


Fig.  211.     Cutter  with  Inserted  Teeth 

Courtesy  of  Becker  Milling  Machine  Company, 

Hyde  Park,  Massachusetts 


140 


MACHINE  SHOP  WORK 


by  breakage  when  hardening.  To  make  an  economical,  serviceable 
cutter  of  large  size,  it  is  customary  to  use  a  cast-iron  body  with 
inserted  tool  steel  teeth.  There  are  several  different  methods  of 
inserting  and  holding  these  teeth.  Usually,  when  the  inserted  tooth 


Fig.  212.     Form  of  Inserted-Tooth  Cutter  Called  Slabbing  Cutter 

is  in  the  form  of  a  blade,  they  are  held  by  taper  pins  or  screws, 
Fig.  211.  These  blades  are  renewable,  the  cast-iron  body  being  used 
many  times. 

Another  form  of  inserted-tooth  cutter  consists  of  round,  hard- 
ened steel  pins  driven  into  holes  in  a  cast-iron  body.  This  cutter  is 
also  permanent  in  form,  Fig.  212,  as  broken  teeth  cannot  be  replaced; 
and,  when  the  teeth  are  worn  almost  down  to  the  body,  the  whole 
cutter  is  thrown  away. 

Form  Cutters.  Brief  mention  has  been  made  of  cutters  to 
generate  irregular  contours.  These  cutters  are  known  as  form 
cutters,  and,  except  in  certain  shapes,  such  as  quarter-  and  half- 
rounds,  are  not  carried  in  stock,  but  are  made  only  to  order.  There 
is  such  a  large  variety  of  forms  for  which  such  cutters  may  be  used 


Fig.  213.    Gang  of  Form  Cutters 


that  it  is  impossible  to  give  more  than  typical  examples.  The 
form  shown  in  Fig.  213  consists  in  reality  of  several  cutters,  some  of 
them  of  ordinary  shapes  and  sizes,  with  others  of  special  forms,  the 
whole  making  a  gang  cutter  whose  object  is  very  apparent. 


MACHINE  SHOP  WORK 


141 


Among  the  standard  shapes  of  form  cutters  are  some  which 
are  now  carried  in  stock  for  producing  certain  tools  requiring  cutters 
of  definite  yet  peculiar  form.  Among  these  may  be  mentioned  cut- 


SPROCKET  CUTTSKS. 


TWIST  DRILL    CUTTER.  GEAR   TOOTH 

Fig.  214.     Standard  Shapes  of  Form  Cutters 

ters  for  fluting  taps,  reamers,  and  twist  drills;  cutters  for  sprocket 
and  gear  teeth;  and  cutters  known  as  hobs,  for  the  production  of 
worm  gears,  Fig.  214. 


142 


MACHINE  SHOP  WORK 


End  Mills.    All  the  cutters  thus  far  mentioned  are  provided 
with  central  holes,  and  are  intended  to  be  mounted  on  an  arbor 


Fig.  215.     Ordinary  Form  of  End  Mill 
Courtesy  of  Becker  Milling  Machine  Company,  Hyde  Park,  Massachusetts 

which  is  carried  by  the  milling  machine  spindle  and  supported  in 
some  suitable  manner  at  the  outboard  end.  There  is  an  entirely  dif- 
ferent class  of  cutters, 
however,  which  are  sup- 
ported by  the  spindle 
only,  and  which  are  pro- 
vided with  teeth  at  the 

Fie.  216.    T-Siot  Milling  Cutter  and  Section  of  Slot        Cnd  °f  the  CUttef-    TheS6 

are  known  as  end  mills. 

They  are  made  in  a  great  variety  of  shapes  and  sizes,  the  ordinary 
end  mill,  Fig.  215,  being  cylindrical,  with  either  a  right-  or  left- 
hand  spiral. 

T-Slot  Cutter.  A  special 
form  of  end  mill  for  making 
T-slots  is  called  the  T-slot  cut- 
ter, and  is,  in  reality,  a  small 
side  milling  cutter  carried  by  a 
small  central  stud,  as  shown  in 
Fig.  216. 


Fig.  217.    Dovetail  Milling  Cutter 


Fig.  218.     End  Mill  with  Inserted  Teeth 

Courtesy  of  Becker  Milling  Machine  Company, 

Hyde  Park,  Massachusetts 


Dovetail  Cutters.  Dovetail  cutters,  Fig.  217,  and  cutters  of  various 
angles  for  making  ratchets,  are  merely  variations  of  the  end  milL 


MACHINE  SHOP  WORK 


143 


Fig.  219.     Taper  Collet 


When  end  mills  are  made  of  large  size,  they  can  be  furnished 
with  inserted  teeth,   Fig.   218,   similar  to  those  described.     The 
heaviest   end   mills  for 
the    milling  machine 
are  sometimes  made 
as    large    as  fifteen   to 
twenty  inches  in  diam- 
eter, the  cast-iron  body  being  screwed  directly  onto  the  nose  of  the 
spindle,  making  a  very  powerful  and  fast-cutting  tool. 

Methods  of  Mounting  Milling  Cutters.  The  plain  milling  cutter 
is  mounted  on  an  arbor  in  a  way  very  similar  to  that  in  which  its 
spindle,  prototype,  the  circular  saw,  is  mounted. 

Where  the  cutter  teeth  are  formed  integral  with,  or  fastened  to, 
the  taper  shank,  as  in  the  case  of  end  mills,  the  shank,  if  it  be  of  a 
proper  size,  is  placed  directly  into  the  taper  hole  in  the  spindle. 
In  many  cases,  however,  the  taper  shank  of  the  cutter  is  much  too 
small  to  fit  the  spindle  hole;  and  taper  collets,  Fig.  219,  are  used  to 
bush  down  the  spindle  hole  to  the  proper  size.  Of  course,  it  is 
necessary  that  the  axes  of  the  outer  and  inner  tapers  should  coincide; 
otherwise  the  cutter  will 
not  run  true.  In  some 
cases  it  is  necessary 
to  use  two  collets,  one 
within  the  other,  before 
introducing  the  cutter 
shank. 

When  shell  end  mills, 
Fig.  220,    are    used,    a 
special    form    of    taper 
shank  is  employed  which 
can  take  several  different     Fi8/220'   She"  End  ^n  and  Tape,  shank,  or  Holding  it 
sizes  of  cutters.    The  construction  is  so  obvious  from  the  illustration 
that  explanation  is  unnecessary. 

End  mills,  having  taper  shanks,  rely  largely  on  the  friction  of 
the  taper  for  holding  in  position-,  although  being  driven  by  a  tongue 
at  the  end  of  the  shank.  Therefore  cutters  of  this  description  should 
not  have  a  spiral  in  a  direction  which  would  tend  to  pull  the  cutter 
out.  This  is  not  a  serious  objection  when  using  the  cylindrical  portion 


144 


MACHINE  SHOP  WORK 


of  the  cutter;  but  when  using  the  end  of  the  cutter,  it  means  that  the 
teeth  can  have  no  rake,  and  must  scrape  rather  than  cut  the  work. 
In  order  to  use  a  leading  spiral  on  the  cutter,  the  shank  must  be  held 
positively  in  the  spindle.  This  usually  is  accomplished  by  inserting 
in  a  threaded  hole  at  the  rear  end  of  the  shank,  a  rod  which  extends 
through  the  hollow  spindle  and  brings  up  against  a  collar  on  the  out- 
side. This  can  be  set  up  solidly,  and  all  danger  of  loosening-up  of 
the  cutter  shank  will  be  avoided. 

When  the  cutter  is  small,  as  compared  with  the  diameter  of  the 
spindle  taper,  a  screw  collet  may  be  used,  as  the  friction  of  the  collet 

will  be  greater  than  the  tendency  of 
the  leading  spiral  to  move  the  cutter 
from  the  spindle.  These  screw  collets 
are  commonly  made  of  machine  steel, 
while  the  end  mills  are  made  from 
tool  steel.  The  short,  steep  taper 
and  threaded  end  are  shorter  than 
the  long  taper  shank,  resulting  in  a 
cheaper  cutter. 

One  of  the  best  means  for  hold- 
ing small  end  mills  with  straight 
teeth  is  by  the  use  of  spring  collets, 
Fig.  221,  which  can  firmly  grasp  the 
straight  shank  of  the  cutter.  When 
cutters  are  to  be  changed  frequently, 
this  is  a  particularly  satisfactory 
method,  although  it  will  not  answer  for  roughing  cuts  where  cutters 
of  large  diameter  are  used,  as  the  torque  will  be  too  great  for  the 
jaws  of  the  collet  to  prevent  turning. 

An  ordinary  drill  chuck  can  be  held  in  the  spindle  by  means  of 
a  taper  shank,  and  furnish  a  means  of  holding  straight-shank  drills 
and  other  small  straight-shank  tools. 

A  very  convenient  method  of  holding  certain  tools  consists  in 
fitting  a  three- jawed  universal  lathe-chuck  to  the  threaded  nose  of 
the  spindle,  thus  enabling  straight-shank  tools  of  large  size  to  be  held 
firmly  and  accurately.  Cutters  of  any  kind  are  rarely  held  in  chucks 
on  the  milling  machine,  but  a  large  number  of  other  small  tools  can 
be  held  advantageously. 


Fig.  221.     Typical  Spring  Collets 


MACHINE  SHOP  WORK 


145 


TYPES  OF  MILLING  MACHINES 

Bench  Miller.    In  taking  up  the  subject  of  machines  devoted 
especially  to  milling,  it  is  well  to  consider  that  the  transition  from 


Fig.  222.     Rivett  Lathe  with  Milling  Attachment 
Courtesy  of  Rivett  Lathe  Manufacturing  Company,  Boston,  Massachusetts 

milling  in  the  lathe  to 
the  special  milling  ma- 
chine was  bridged  by  an 
attachment  to  the  lathe 
by  which  the  functions 
of  the  milling  machine 
are  well  served.  This  is 
especially  noticeable  in 
the  milling  attachment 
attached  to  bench  lathes, 
Fig.  222,  said  attach- 
ment being  mounted  on 
the  bed  of  the  lathe  and 
the  spindle  provided 
with  a  milling  cutter. 
This  arrangement  is 
used  for  simple  milling  operations.  Such  devices  led  to  the  intro- 
duction of  the  bench  miller,  Fig.  223,  which  is  naturally  intended  for 
small  work  only,  and  therefore  is  not  provided  with  automatic  feeds, 
hand-feeding  by  means  of  levers  being  used. 


Fig.  223.     Bench  Miller 


146 


MACHINE  SHOP  WORK 


Horizontal  Milling  Machine.  The  horizontal  milling  machine, 
Fig.  224,  consists  of  a  frame  or  box  structure  carrying  a  horizontal 
spindle  in  the  upper  portion,  together  with  brackets  or  an  over- 
hanging arm  to  steady  the  spindle.  The  front  of  the  frame  is  care- 
fully machined  and  hand-scraped  at  right  angles  to  the  spindle;  and 
there  is  mounted  on  the  front  a  knee,  the  upper  surface  of  which  is 
parallel  to  the  spindle  in  the  horizontal  plane  and  capable  of  move- 


Fig.  224.     Horizontal  Milling  Machine — Column  Type 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  island 


ment  in  a  vertical  direction.  This  knee  carries  what  is  known  as  the 
saddle,  the  upper  portion  of  which  is  also  parallel  to  the  spindle. 
The  movement  of  the  saddle  is  toward  and  from  the  frame  of  the 
machine,  and  therefore  parallel  to  the  spindle.  The  saddle,  in  turn, 
carries  the  table,  to  which  the  work  is  attached  by  means  that  will 
be  described.  The  upper  surface  of  the  table  is  parallel  to  the  spindle, 
and  the  table  movement  is  at  right  angles  to  the  spindle  in  the 
horizontal  plane. 


MACHINE  SHOP  WORK 


147 


The  combination  of  these  three  motions  at  right  angles  to  the 
spindle  in  the  vertical  plane,  parallel  to  the  spindle  in  the  horizontal 
plane,  and  at  right  angles  to  the  spindle  in  the  horizontal  plane,  gives 
to  the  milling  machine  what  is  known  as  its  range.  It  allows  any 
portion  of  the  table  to  be  brought  under  the  cutter  at  any  distance 
covered  by  the  vertical  feed. 

Micrometer  Graduations.  It  will  be  seen,  therefore,  that  one  of 
the  principal  advantages  of  the  milling  machine  is  its  wide  range 


Fig.  225.     Slabbing  Miller— Planer  Type 
Courtesy  of  Ingersoll  Milling  Machine  Company,  Rockford,  Illinois 

of  working  capacity,  and  the  accuracy  with  which  the  table  can  be 
placed  with  relation  to  the  cutter.  This  accuracy  is  obtained  by  means 
of  graduated  dials  on  the  feed-screws,  which  are  read  directly  to 
.001  inch,  and,  by  estimation,  to  .00025  inch.  For  many  years  the 
milling  machine  was  the  only  tool  which  supplied  these  micrometer 
graduations,  but  they  are  now  applied  to  nearly  every  class  of  machine 
tool  in  which  accurate  adjustment  is  necessary.  A  common  method 
of  graduation  is  by  the  use  of  a  screw  with  a  pitch  of  ^  inch 


148 


MACHINE  SHOP  WORK 


and  with  200  graduations  on  its  dial.  In  some  cases,  a  screw  with 
a  pitch  of  J  inch  is  used  with  250  graduations,  but  it  is  always  safe 
to  assume  that  the  single  graduation  on  a  milling  machine  means  a 
movement  of  .001  inch 

Avoiding  Backlash  Error.  Lost  motion  or  backlash  between  the 
screw  and  its  nut,  in  any  of  these  adjustments,  is  a  cause  of  frequent 
error,  and  should  always  be  considered.  Even  for  a  machine  in 


Fig.  226.     Planer  Type  Four-Spindle  Milling  Machine 
Courtesy  of  Ingersoll  Milling  Machine  Company,  Rockford,  Illinois 

excellent  condition,  when  the  motion  of  the  screw  is  reversed,  the 
screw  will  turn  through  an  angle  giving  the  equivalent  of  about 
.005  inch  movement  of  the  part  being  fed  along,  but  with  no  actual 
movement  of  the  part.  As  an  example,  if,  in  moving  the  table  from 
the  column,  the  operator  carries  it  .003  inch  too  far,  it  will  not  suffice 
simply  to  turn  the  dial  back  three  graduations.  The  table  should  be 
brought  back  several  hundredths  of  an  inch,  and  again  advanced  to 
within  .003  inch  of  its  former  position.  In  order  to  facilitate  the 


MACHINE  SHOP  WORK 


149 


quick  and  accurate  reading  of  these  dials,  they  are  arranged  so  that 
they  can  be  readily  set  to  zero  whenever  desired. 

Distinction  between  Plain  and  Universal  Millers.  The  move- 
ments above  described  for  the  adjustment  of  the  work  are  those 
necessary  for  what  is  termed  a  plain  milling  machine.  In  order  to 


have  a  universal  milling  machine,  Fig.  224,  it  is  necessary  that  the 
table  be  so  arranged  that  it  can  be  swung  upon  the  saddle  in  the 
horizontal  plane,  so  that  its  feeding  movement  is  not  at  right  angles 
to  the  axis  of  the  spindle,  Universal  milling  machines  usually  have 


150 


MACHINE  SHOP  WORK 


a  total  working  angular  movement  of  90  degrees,  45  degrees  on 
either  side  of  the  normal  position. 

While  the  milling  machine  developed  from  the  lathe,  through  the 
Lincoln  miller,  to  the  standard  horizontal  universal  machine,  its 
development  for  work  on  which  heavy  cuts  are  necessary  took  an 
opposite  course. 

Planer  Type  Milling  Machines.  The  slabbing  miller,  Fig.  225, 
is  of  the  planer  type,  the  cross-rail  carrying  a  rigidly  supported  cutter, 
while  the  table  has  the  comparatively  slow  feed  required  for  milling. 
This  type  of  machine  is  especially  valuable  wiiere  broad  surfaces  are 
to  be  machined  on  pieces  of  work  which  are  of  such  shape  that  they 
can  be  readily  and  uniformly  supported  to  withstand  the  cut. 

Another  milling  machine  of 
the  planer  type,  having 
four  spindles,  is  shown  in 
Fig.226.  It  is  designed  for 
very  hesavy  work. 

Especial  Care.  Neces- 
sary to  Keep  Work  True.  In 
order  to  produce  true  work 
by  heavy  milling,  it  is  not 
only  necessary  x  that  the 
work  shall  be  supported  as 
already  outlined,  but  also 
that  the  cut  be  nearly  uni- 

Fig.  228.     End  Milling  Attachment  on  Planer  form    in    deDth    and   width 

If  the  section  of  the  cut  varies  greatly,  or,  even  with  uniform  cut,  if 
the  work  is  irregularly  supported,  the  metal  will  spring  under  the 
influence  of  the  cutter,  and  it  will  be  found  that  the  work  is  not 
true.  Therefore,  work  of  a  character  that  from  its  shape  is  especially 
liable  to  be  distorted  by  the  process  of  milling,  may  be  machined  to 
better  advantage  by  the  process  of  planing. 

Milling  Attachments  for  Planer.  It  is  often  desirable,  from  the 
point  of  view  of  economy  of  time,  to  combine  the  operations  of  milling 
and  planing,  and,  with  this  end  in  view,  milling  attachments  are  made 
for  the  planer  in  a  single  machine,  Fig.  227,  and  attached  to  the  cross- 
rail.  The  changes  required  from  the  planer  drive,  are  an  extra  belt 
to  rotate  the  cutter,  and  a  special  countershaft  to  slow  down  the  move- 


MACHINE  SHOP  WORK  151 

ment  of  the  table.  This  attachment  can  carry  a  slabbing,  gang,  or 
formed  cutter  on  an  arbor  for  horizontal  milling;  or  it  can  carry  end 
mills,  Fig.  228,  by  turning  the  attached  head  through  90  degrees, 
thus  bringing  the  spindle  to  a  vertical  position.  This  last  arrange- 
ment of  the  spindle  is  of  great  utility,  as  it  allows  cutters  to  reach 
down  into  places  which  would  be  inaccessible  by  any  other  means. 
Vertical  Milling  Machines.  Vertical  Head  on  Horizontal 
Machines\  The  advantages  of  the  vertical  milling  spindle  are  so 


Fig.  229.     Vertical  Milling  Head  Attached  to  Horizontal  Milling  Machine 

Courtesy  of  Brown  and  Sharpe  Manufacturing  Company, 

Providence,  Rhode  Island 

evident  that  nearly  all  makers  of  horizontal  machines  furnish  what  is 
called  a  vertical  head,  Fig.  229.  This  vertical  head  is  very  rigidly 
supported  on  the  column  by  means  of  the  overhanging  arm,  so 
that  cuts  can  be  taken  of  as  great  depth  as  with  the  horizontal 
spindle.  The  vertical  spindle  can  also  be  turned  in  the  vertical  plane, 
so  that  an  end  mill  can  be  used  at  any  angle  with  the  table. 

Vertical  Spindles  Only.  There  are  several  machines  made  in 
which  the  vertical  spindle  alone  is  employed,  Fig.  230,  there  being 
no  provision  for  a  horizontal  spindle. 


152  MACHINE  SHOP  WORK 

Such  machines  are  provided  with  the  feed  motions  of  the 
horizontal  type,  and  also  with  a  rotating  table  by  which  circular 
work  can  be  done.  A  large  amount  of  work  formerly  done  in  lathes 


Fig.  230.     Vertical  Milling  Machine  with  Working  Parts  Shown  in  Ghost 
Courtesy  of  Becker  Milling  Machine  Company,  Hyde  Park,  Massachusetts 

is  now  being  done  in  vertical  spindle  machines,  as  well  as  many 
pieces  formerly  machined  on  planers  and  shapers. 

Duplex  Milling  Machines.  The  duplex  milling  machine, 
Fig.  231,  has  both  the  horizontal  and  vertical  spindles  combined  in 
one,  which  allows  the  spindle  to  be  placed  at  any  angle  from  horizontal 
to  vertical,  and  combines  all  the  good  points  of  both  machines.  The 


MACHINE  SHOP  WORK 


153 


head  of  the  duplex  miller  can  be  moved  out  over  the  table  so  as  greatly 
to  increase  the  range  of  the  machine;  and  this  head  is  also  provided 
with  a  drilling  attachment  whereby  holes  may  be  drilled  at  any  angle. 


Fig.  231.     Duplex  Milling  Machine  Set  for  Cutting  Spiral 
Courtesy  of  Van  Norman  Machine  Tool  Company,  Springfield,  Massachusetts 

MILtINQ  OPERATIONS 

Classification.  These  may  be  classified  in  a  manner  similar  to 
the  cutters  themselves,  whose  names  will  suggest  the  kind  of  work  for 
which  they  are  adapted. 

Plane  Milling  or  Surface  Milling.  This  is  the  machining  of 
plain,  flat,  horizontal  surfaces  by  means  of  cylindrical  mills  whose 
length  is  usually  much  greater  than  their  diameters,  the  larger  kinds 
being  constructed  with  inserted  blades  or  teeth. 

Side  Milling  or  Face  Milling.  This  operation  is  the  machining 
of  vertical  surfaces,  or  surfaces  at  right  angles  to  the  axis  of  the 
milling  cutter. 


154  MACHINE  SHOP  WORK 

Angle  Milling.  As  the  name  suggests,  this  is  the  machining  of  a 
surface  at  some  other  than  a  right  angle  to  the  axis  of  the  milling  cutter. 

Form  Milling.  The  machining  of  some  special  cross-section 
generally  composed  of  straight  lines  and  curves,  or  wholly  of  curves, 
is  called  form  milling. 

Profiling.  This  operation  is  usually  considered  as  machining 
the  vertical  edges  of  pieces  of  irregular  contour,  and  is  generally  done 
with  an  end  mill  mounted  in  a  vertical  spindle.  The  exact  form  is 
generally  determined  by  a  templet  or  profile  attached  to  the  piece 
or  to  the  fixture  supporting  it. 

Care  of  Milling  Cutters.  This  is  a  matter  of  much  importance, 
since  a  worn  or  dull  cutter  will  never  produce  good  work,  and  a  good 
cutter  is  soon  spoiled  by  improper  use  or  lack  of  care  in  handling. 
The  cutting  edge  should  always  be  sharp  and  keen;  but  it  is  of  still 
greater  importance  that  each  edge  should  be  exactly  the  same  distance 
from  the  axis  of  rotation — or,  in  other  words,  that  the  cutters  should 
run  true.  When  this  condition  does  not  exist,  the  greater  part  of  the 
work  will  fall  upon  two  or  three  of  the  teeth,  and  these  wrill  be 
speedily  ruined,  while  the  others  do  little  or  no  work. 

Care  should  be  taken  to  have  the  arbor  run  true;  otherwise  a 
cutter -that  is  ground  true  will  not  run  so.  Therefore,  cutter  arbors 
should  be  examined  and  tested  frequently  to  see  that  the  portion 
upon  which  the  cutter  or  loose  collars  rest  runs  true  and  is  smooth, 
and  not  defaced  by  bruises  from  rough  handling. 

Grinding  Milling  Cutters.  A  good  cutter-grinding  machine  is 
absolutely  essential.  It  should  have  a  well  fitted  and  true  spindle, 
and  such  attachments  for  holding  cutters  of  various  kinds  as  to  be 
able  to  grind  all  the  usual  forms  without  important  changes  of 
mechanism.  The  centers  for  supporting  arbors,  and  the  devices  for 
holding  cutters  not  on  arbors,  should  be  well  fitted  and  true.  The 
machine  should  be  equipped  with  such  graduated  circles  as  will 
enable  the  operator  readily  to  set  it  for  grinding  all  the  usually 
required  angles. 

Fig.  232  shows  a  regular  machine  for  this  purpose.  It  is  so 
arranged  that  various  forms  of  cutters  can  be  ground  either  when 
mounted  upon  cutter  arbors  or  held  in  the  machine  fixture  provided ; 
and  it  has  a  number  of  well-designed  attachments  by  which  a  con- 
siderable amount  of  general  grinding  can  be  successfully  done. 


MACHINE  SHOP  WORK 


155 


In  keeping  milling  cutters  in  order,  they  should  be  ground  as 
soon  as  they  become  dulled,  whether  wanted  for  immediate  use  or 
not.  It  is  more  economical  to  have  them  always  ready,  as  the 
emergency  is  likely  to  occur  at  a  time  when  a  cutter  is  wanted  at 
once,  and  when  there  is  not  time  to  grind  it  properly. 

Cutters  should  be  kept  sharp.  A  dull  cutter  will  not  only  wear 
away  more  rapidly  than  a  sharp  one,  but  it  will  also  do  poor  work; 


Fig.  232.     "Cincinnati"  No.  2  Universal  Cutter  and  Tool  Grinder 
Courtesy  of  Cincinnati  Milling  Machine  Company,  Cincinnati,  Ohio 

it  will  take  a  great  deal  more  power  to  drive  it,  and  the  milling 
machine  wrill  be  more  rapidly  worn  out. 

Care  should  be  taken,  in  grinding  angular  cutters,  that  the 
points  are  not  heated  so  as  to  draw  the  temper.  This  very  easily 
happens  if  considerable  care  is  not  used,  the  cutting  edges  becoming 
so  softened  as  to  be  rapidly  worn  away  and  the  cutter  spoiled  by  use. 
Formed  cutters  are  frequently  affected  in  a  similar  manner.  The 
excessive  friction  of  a  dull  cutter  will  frequently  generate  a  sufficient 
amount  of  heat  to  draw  the  temper  of  the  teeth  at  the  cutting  edge. 


156  MACHINE  SHOP  WORK 

In  making  the  grinding  machine  ready  to  grind  a  cutter,  it  is 
necessary  to  see  that  the  emery  wheel  runs  perfectly  true;  and  if  it 
does  not,  it  should  be  trued  up  before  any  grinding  work  is  done. 
If  the  cutter  is  to  be  sharpened  upon  an  arbor,  the  latter  should  be 
tested  to  ascertain  if  it  runs  true  before  putting  the  cutter  on  it. 
In  grinding  the  cutter,  light  grinding  cuts  should  be  taken,  and  the 
cutter  moved  rapidly  across  the  face  of  the  wheel.  The  wheel  should 
be  the  proper  grade  of  emery,  not  finer  than  90,  nor  coarser  than  56. 
The  coarser  and  softer  the  wheel,  the  higher  may  be  the  speed.  It  is 
not  advisable  to  make  the  speed  over  4,500  feet  per  minute  at  the 
outer  edge  of  the  wheel.  The  cutting  edge  of  the  wheel  need  not  be 
over  an  eighth  of  an  inch  thick,  in  any  case. 

Preparing  the  Milling  Machine  for  Work.  The  taper  shank 
of  the  arbor  and  the  hole  in  the  spindle  should  be  wiped  clean  and 
free  from  oil  or  grit.  Should  the  outer  end  of  the  arbor  be  sup- 
ported by  a  pointed  center  or  a  bushing,  it  will  not  be  difficult  to 
keep  it  in  place;  but  if  not  so  supported,  it  must  be  driven  tightly  into 
the  spindle,  using  care  that  the  flattened  end  or  tang  fits  perfectly 
into  the  slot  provided  for  it.  If  it  is  noticed  that  the  arbor  does  not 
fit  fairly  into  the  spindle,  it  should  be  removed  and  examined  to  see 
that  there  are  no  dents  or  bruises  on  it,  and  that  the  tang  is  not  too 
long  or  too  thick,  or  the  shoulders  not  cut  back  far  enough  to  permit 
it  to  fit  properly.  When  arbors  work  loose,  it  is  on  account  of  some 
one  of  these  causes. 

If  the  arbor  does  not  run  true  when  the  cutter  is  mounted  and 
the  clamp-nut  screwed  up,  the  nut  and  collars  should  be  removed 
and  examined.  Fine  chips  or  dirt  are  likely  to  be  found  between 
the  collars,  or  between  them  and  the  cutter,  causing  the  arbor  to 
spring  when  the  clamp  nut  is  screwed  up.  The  parts  should  be 
cleaned  and  again  put  in  place. 

Cutting  Speeds.  Conditions  Governing  Speed.  There  are  no 
hard  and  fast  rules  that  will  properly  govern  a  majority  of  cases  of 
the  continually  varying  conditions  of  milling  cutters,  machines,  and 
the  material  to  be  machined.  In  any  case,  much  must  be  left  to  the 
judgment  of  the  foreman  and  the  operator.  Prominent  among  the 
conditions  that  tend  to  vary  the  cutting  speed  are  the  following : 

The  cutter  may  be  newly  ground,  keen,  and  sharp;  or  it  may  have  been 
considerably  dulled  by  use.  While  not  dull  enough  to  require  grinding,  it  will 


MACHINE  SHOP  WORK  157 

not  be  safe  to  run  it  up  to  the  speed  of  a  sharp  cutter.  The  teeth  may  be  worn 
thin  from  long  use  and  re-grinding,  and  not  strong  enough  to  stand  the  strain 
of  maximum  speed.  The  cutter  may  be  of  such  a  form — as  a  double-angle 
cutter — that  the  teeth  will  not  bear  the  strain  of  full  speed. 

The  machine  may  be  well  designed  and  built,  and  free  from  vibration;  or 
it  may  be  directly  the  reverse,  a  fast  speed  producing  so  much  chattering  as  to 
spoil  both  work  and  cutter.  The  arbor  may  be  large  and  stiff,  or  small  and 
slender.  In  one  case,  a  fast  speed  may  be  maintained;  and  in  the  other,  both 
work  and  cutter  would  suffer.  The  driving  gearing  may  be  well  designed  and 
its  teeth  fit  accurately  with  no  backlash;  or  it  may  be  poorly  designed  and 
made,  or  much  worn,  and  cause  much  chattering  on  a  fast  speed.  There  are 
many  other  similar  conditions. 

The  material  may  be  of  varying  degrees  of  hardness  and  toughness,  and  of  a 
great  variety  of  forms.  Some  iron  castings  will  be  more  severe  on  a  cutter 
than  tool  steel  would  be.  The  scale  on  cast  metal  is  very  hard  to  cut  through, 
and  dulls  the  teeth  of  a  cutter  quickly.  The  varying  hardness  of  steel,  from 
that  ordinarily  found  in  the  bar  to  that  properly  annealed,  is  great.  The  amount 
of  carbon  in  steel  is  always  a  varying  condition  for  which  it  is  difficult  to  formu- 
late rules.  Therefore  it  is  only  possible  to  give  rules  that  will  meet  a  fair  average 
of  conditions. 

In  order  to  accommodate  different  sizes  of  cutters,  maintain  a 
uniform  cutting  speed,  and  also  allow  for  difference  in  hardness  of 
the  material  being  worked,  it  is  necessary  that  the  milling  machine 
should  be  supplied  with  several  speeds.  In  the  ordinary  miller  we 
usually  have  a  four-step  cone  with  back  gears,  which  gives  eight 
speeds  with  a  single  overhead  belt.  The  countershafts  for  these 
machines  are  of  the  friction  type,  and  are  supplied  with  two  driving 
pulleys  driving  in  the  same  direction,  but  at  different  speeds,  giving  a 
total,  including  the  back  gears,  of  sixteen  speeds  for  each  machine. 

Form  of  Cutter  as  Affecting  Its  Speed  and  Feed.  A  slitting  cutter 
(practically  a  saw)  may  be  run  much  faster,  than  one  of  broad  face. 

A  cutter  of  small  diameter  will  cut  faster  than  a  large  one,  as 
the  arc  of  action  is  much  less. 

Angle  cutters  must  be  run  at  lower  relative  speeds  so  as  not  to 
break  off  the  slender  points  of  the  teeth. 

The  speed  may  sometimes  be  profitably  increased  without 
changing  the  rate  of  feed.  Again,  the  speed  should  be  decreased 
according  to  the  conditions  of  the  work. 

There  is  no  direct  and  constant  ratio  between  speed  and  feed. 
Conditions  may  vary  either  one  without  changing  the  other. 

A  roughing  cut  will  often  work  better  with  a  moderate  speed  and 
a  coarse  feed.  The  smoothness  of  the  work  is  not  so  important  as 


158 


MACHINE  SHOP  WORK 


taking  off  the  surplus  stock.    With  a  finishing  cut,  the  conditions 

are  reversed  and  a  fine  feed  is  necessary. 

Cutters  with  inserted  blades  will  not  usually  stand  as  high  a 

speed  as  solid  cutters,  particularly  when  the  blades  have  a  large 

cutting  surface.    This  condition  is  emphasized  when  cutting  rather 

hard  and  tough  material. 

If  there  is  a  comparatively  small  space  for  chips  between  the 

teeth  of  the  cutter,  a  light  cut  must  be  taken,  or  a  slower  feed  used, 

so  that  the  chips  will  not  clog  the  cutter. 
Speed  Used  on  Particular  Work  or 
Material.  The  speed  used  on  any  par- 
ticular work  depends,  as  before  stated, 
on  the  diameter  of  the  cutter  and  the 
character  of  the  work.  Thus,  with  car- 
bon steel  cutters,  the  cutting  speed  will 
be  30  to  60  feet  per  minute.  With  high- 
speed steel  cutters,  double  these  speeds 
may  be  maintained  if  the  drive  of  the 
machine  is  strong  enough  to  pull  the  cut. 
When  using  very  small  cutters,  the 
machine  itself  will  not  usually  give  a 
speed  which  is  high  enough  to  suit  the 
diameter  of  the  cutter.  For  such  work, 
a  high-speed  attachment,  Fig.  233,  is 
furnished,  by  which  the  small,  light 

cutters  may  be  driven  at  a  suitable  rate. 

Of  equal  importance  with  the  correct  speed  for  the  cutter,  is  the 

maximum  feed  or  table  speed,  which  is  reckoned  in  inches  per  minute. 

A  more  logical  method  of  designating  the  feeds,  and  one  which  has 

been  adopted  by  several  makers,  is  to  give  the  advance  of  the  table 

in  thousandths  of  an  inch  for  every  turn  of  the  spindle. 

Based  upon  the  use  of  the  ordinary  carbon  steel  cutters,  the 

Brown  and  Sharpe  Manufacturing  Company   have  prepared  the 

following  statements  regarding  the  speed  of  cutters: 

It  is  impossible  to  give  definite  rules  for  the  speed  and  feed  of  mills.  The 
judgment  of  the  foreman  or  man  in  charge  of  the  machine  should  determine 
what  is  best  in  each  instance. 

As  usually  the  highest  possible  speed  and  feed  are  desirable,  it  pays  to 
increase  them  both  until  it  is  seen  that  something  will  break  or  burn,  and  then 


Fig.  233.     High-Speed  Attachment 
for  Milling  Machine 


MACHINE  SHOP  WORK 


159 


TABLE  IV 
Speeds  and  Feeds  for  Milling  Cutters* 


MATERIAL 

SPEED 
(ft.  per  min.) 

FEED 
(in.  per  min.) 

Soft  cast  iron 

60 

11 

Hard  cast  steel 

40 

Wrought  iron 

45 

1 

Soft  machine  steel 

36 

Hard  machine  steel 

24 

Tool  steel,  annealed 

30 

Tool  steel,  not  annealed 

20 

Soft  brass 

120 

2 

Hard  brass 

100 

2 

Bronze 

80 

1 

Bronze,  gun  metal 

60 

Vulcanized  fiber  (gray  and  red) 

60 

6& 

reduce  to  a  speed  and  feed  of  safety.  Sometimes  the  speed  must  be  reduced, 
and  yet  the  feed  need  not  be  changed. 

The  average  speed  on  wrought  iron  and  annealed  steel,  using  carbon  steel 
cutters,  is  perhaps  40  feet  per  minute,  which  gives  about  sixty  turns  per  minute 
with  mills  2£  inches  in  diameter.  The  feed  of  the  work  for  this  surface  speed 
of  the  mill  can  be  about  1|  inches  per  minute,  and  the  depth  of  the  cut  about 
Y^  inch.  In  cast  iron,  a  mill  can  have  a  surface  speed  of  about  50  feet  a  minute 
while  the  feed  is  1|  inches  per  minute  and  the  cut  YS  mch  deep.  In  tough  brass, 
the  speed  may  be  80  feet,  the  feed  the  same  as  in  cast  iron,  and  the  chip  -fe  inch. 

As  small  mills  cut  faster  than  large  ones,  an  end  mill,  for  example,  \  inch 
in  diameter,  can  be  run  about  400  revolutions  per  minute  with  a  feed  of  4  inches. 

Addy,  an  English  authority,  gives  as  a  safe  speed  for  cutters  of 
6  inches  diameter  and  upward : 

Steel,  36  ft.  per  min.,  with  a  feed  of  \  in.  per  min. 
Wrought  iron,  48  ft.  per  min.,  with  a  feed  of  1  in.  per  min. 
Cast  iron,  60  ft.  per  min.,  with  a  feed  of  If  in:  per  min. 
Brass,  120  feet  per  min.,  with  a  feed  of  2|  in.  per  min. 

He  also  gives  a  simple  rule  for  obtaining  the  speed: 
The  number  of  revolutions  which  the  cutter  should  make  when  working 
on  cast  iron  equals  240  divided  by  the  diameter  in  inches. 

In  Table  IV  are  given  the  average  speeds  in  feet  per  minute 
of  the  periphery  of  the  cutter,  and  the  rate  of  feed  in  inches  per 
minute  for  various  materials. 

Tables  V,  VI,  VII,  and  VIII,  have  been  prepared  by  the 
Brown  and  Sharpe  Manufacturing  Company,  to  give  the  speed, 
feed,  and  depth  of  cut  that  can  be  obtained  with  a  machine  similar 
to  that  illustrated  in  Fig.  224.  It  is  understood  that  these  speeds 

*Attention  is  called  to  the  seemingly  slow  speed  and  fast  feed  for  vulcanized  fiber. 
Practice,  however,  proves  it  to  be  correct. 


160 


MACHINE  SHOP  WORK 


TABLE  V 
Surface  Milling  of  Cast  Iron 


FEED  PER  MINUTE 

DIAMETER 
OF  MILL 
(in.) 

REVOLUTIONS 
PER  MINUTE 

OPEED  OF 

CUTTER 
PER  MINUTE 
(ft.) 

DEPTH  OF 
CUT 
(in.) 

WIDTH  OF 

CUT 
(in.) 

In  Scale 
of  Cast 
Iron 

Under 
Scale  of 
Cast  Iron 

(in.) 

(in.) 

42 
42 

34 
34 

f 

1 
1 

6f 
M 

8| 

3 

42 
42 

34 
34 

! 

2 
2 

6f 
2? 

8| 

42 

34 

3 

6f 

s| 

42 

34 

A 

3 

If 

8| 

42 
42 

40 
40 

* 

8 

2! 

II 

42 

50 

i 

2 

41 

Qi 

42 

50 

i 

4 

31 

41 

41 

42 

50 

i 

6 

2 

2i 

42 

50 

i 

6 

4i 

6? 

42 

50 

tt  ' 

12 

l! 

2 

TABLE  VI 
Surface  Milling  of  Soft  Machinery  Steel 


FEED  PER  MINUTE 

DIAMETER 
OF  MILL 
(in.) 

REVOLUTIONS 
PER  MINUTE 

SPEED  OF 
CUTTER 
PER  MINUTE 
(ft.) 

DEPTH  OF 
CUT 
(in.) 

WIDTH  OF 
CUT 
(in.) 

In  Scale 
of  S.M.S. 

Under 
Scale  of 
S.M.S. 

(in.) 

(in.) 

38 

30 

A 

1 

6 

8 

38 

30 

1 

1 

U 

U 

38 

30 

JL. 

2 

2f 

3^ 

38 

30 

\ 

2 

1 

H 

38 

38 

30 
30 

t 

3 
3 

H 

if 

38 

35 

^ 

8 

11 

3 

2 

38 

35 

1 

8 

1 

H. 

25 

30 

JL 

3 

4 

5 

25 

30 

A 

5 

2| 

4f 

4^ 

25 

30 

f 

5 

i 

25 

30 

A 

10 

If 

2J 

25 

30 

& 

10 

i 

8 

and  feeds  are  those  used  when  the  milling  cutters  are  made  from  a 
good  grade  of  carbon  tool  steel.  If  the  cutters  used  are  made  from 
the  newer  high-speed  steels,  these  figures  can  be  decidedly  increased. 


MACHINE  SHOP  WORK 

TABLE  VII 
End  or  Face  Milling  of  Cast  Iron 


161 


FEED  PER  MINUTE 

DIAMETER 
OF  MILL 

(in.) 

REVOLUTIONS 
PER  MINUTE 

CUTTER 
PER  MINUTE 

(ft.) 

DEPTH  OF 
CUT 

(in.) 

WIDTH  OF 
CUT 

(in.) 

In  Scale 
of  Cast 
Iron 

Under 
Scale  of 
Cast  Iron 

(in.) 

(in.) 

i 

382 

50 

_L 

i 

23 

35 

2 

382 

50 

i 

1 

7 

11 

191 

50 

A 

1 

30 

40 

1 

191 

50 

1 

3 

5* 

If 

109 
109 

50 
50 

4 

If 
If 

17 
3| 

23 
41 

5 

42 

55 

1 

5 

2| 

4| 

16 

10 

45 

1 
4 

16 

I 

1 

TABLE  VIII 
Face  Milling  of  Soft  Machinery  Steel' 


FEED  P^R  MIXUTE 

DIAMETER 
OF  MILL 

(in.) 

DEVOLUTIONS, 
PER  MINUTE 

SPEED  OF 
CUTTER 
PER  MINUTE 

(ft,) 

DEPTH  OF 
CUT 

(in.) 

WIDTH  OF 
CUT 

(in.) 

In  Scale 
of  S.  M.  S. 

Under 
Scale  of 
S.  M   S. 

• 

(in.) 

(in.) 

i 

237 

35 

jL 

} 

2 

267 

35 

i 

1 

1 

152 

40 

I1! 

1 

3 

4f 

152 

40 

1 

, 

87 

40 

h 

If 

2f 

41 

87 

40 

f 

If 

If 

Use  of  Oil  on  Machines  and  Work.  The  milling  machine,  and 
in  fact  all  the  machines  of  the  shop  can  do  efficient  work  only  when 
they  are  well  cared  for.  An  important  element  is  that  they  should 
be  frequently  cleaned  and  well  oiled. 

Great  care  should  be  exercised  that  chips  do  not  get  into  the 
tapered  holes  in  the  spindles  or  between  the  arbor  collars. 

When  at  work  on  steel,  the  milling  cutter  is  kept  flooded  with 
oil  or  a  solution  of  sal  soda,  as  already  specified  for  lathe  work. 


162 


MACHINE  SHOP  WORK 


Oil  is  used  in  milling  to  obtain  smoother  work,  to  make  the 
cutters  last  longer,  and,  where  the  nature  of  the  work  requires,  to  wash 
the  chips  from  the  work  or  from  the  teeth  of  the  cutters.  Some 
lubricant  is  generally  used  in  milling  steel,  wrought  iron,  malleable 
iron,  or  tough  bronze.  Frequently,  when  only  a  few  pieces  are  to 
be  milled,  it  is  not  used,  and  some  steel  castings  are  milled  without  a 
lubricant;  also  in  cutting  cast  iron  it  is  not  used.  For  light,  flat  cuts 
it  is  often  put  on  with  a  brush,  giving  the  work  a  thin  covering  like 
a  varnish.  For  heavy  cuts  it  should  be  led  to  the  mill  from  the  drip 
can  that  is  usually  sent  with  each  machine;  or  it  should  be  pumped 
upon  or  across  the  mill  when  cutting  deep  grooves,  milling  several 
grooves  at  one  time,  or,  indeed,  in  milling  any  work  where,  if  the 
chips  should  stick,  they  might  catch  between  the  teeth  and  sides  of 
the  grooves,  and  scratch  or  bend  the  work. 

The  Brown  and  Sharpe  Manufacturing  Company  recommend  the 
use  of  lard  oil  in  milling.  Any  animal  or  fish  oil,  however,  may  be 
used,  and  then  separated  from  the  chips  by  the  use  of  a  centrifugal 
separator  or  by  dumping  into  a  tank  of  water.  In  the  latter  method, 
the  chips  fall  to  the  bottom  and  the  oil  rises  to  the  top,  whence  it  may 
be  drawn  off  with  but  little  waste. 

Laying  Out  and  Drilling  Holes.  One  of  the  operations  for  which 
the  miller  is  particularly  adapted  is  in  locating  and  drilling  holes 

which  require  accurate  placing. 
The  graduated  feeds  of  the  mill- 
ing machine  allow  the  distances 
to  be  set  off  as  closely  as  .00025 
inch,  and  holes  can  also  be  drilled 
to  a  given  depth  with  equal  accu- 
racy. In  starting  holes,  it  is  best 
to  use  a  spotting  drill,  Fig.  234, 
which  is  extremely  rigid  and  per- 
fectly true.  -The  spot  made  should  be  of  slightly  greater  diameter 
than  the  drill  to  be  used.  The  drill  should  be  what  is  known  as 
reamer  size — that  is,  ^  inch  below  the  standard  —and  the  hole  may 
then  be  reamed,  either  in  one  operation,  using  a  standard  reamer,  or 
by  first  using  a  machine  reamer  which  is  about  .005  inch  under  size, 
to  be  followed  by  the  standard  reamer.  It  is  evident  that  holes 
thus  drilled  and  reamed  will  be  parallel,  and,  by  using  the  vertical 


Fig.  234.     Spotting  Drill 


MACHINE  SHOP  WORK 


163 


head,  holes  can  be  drilled  at  right  angles  in  like  manner.  When 
extreme  accuracy  in  holes  is  demanded,  a  boring  bar  may  be  used  in 
the  spindle  after  the  drill, 
in  order  to  correct  any  error 
due  to  the  running  of  the 
drill  itself. 

Splining  Shafts.  An- 
other operation  suited  to  the 
milling  machine,  although 
sometimes  performed  on  the 
shaper  or  planer,  is  that  of 
splining  shafts.  The  slots 
in  the  table  give  the  proper 
alignment  to  the  shaft;  the 
cutter  can  be  set  with  cor- 
rect relation  to  the  axis 
without  difficulty,  and  the 
spline  cut  full  depth  at  one 
operation.  The  only  objec- 
tion to  this  form  of  spline  is 
the  curve  at  the  end  due  to 
the  shape  of  the  cutter.  An 
end  mill  in  the  vertical  head 
can  be  used  to  remove  this 
objectionable  feature;  and 
some  splining  machines  are 
made,  Fig.  235,  which  per- 
manently carry  both  cut- 
ters, so  that  the  work  can 
be  quickly  shifted  from  one 
to  the  other. 

Making  Dovetails.  The 
operation  of  making  dove- 
tails, which  is  a  delicate  and 
expensive  job  on  a  shaper, 

13  readily  performed   On  the      FiS-  23G-    Dovetail  Cutter  on  Vertical  Milling  Machine 

milling  machine,  especially  of  the  vertical  type,  Fig.  236,  the  cutter 
being  a  form  of  end  mill  suited  to  the  size  and  angle  of  the  dovetail. 


Fig.   235.     Splining   Arrangement  with   End   Mill 
in  Vertical  Head 


164 


MACHINE  SHOP  WORK 


Fig.  237.     Fluting  Taper  Keamor 

Courtesy  of  Van  N'jrman  Machine  Tool  Company, 

Springfield,  Massachusetts 


T-slots  are  cut  in  a  similar  manner,  either  directly  from  the  solid, 
or  by  following  a  groove  made  with  a  plain  cutter. 

Fluting  Taps  and 
Reamers.  One  of  the 
common  operations  per- 
formed between  centers  is 
the  fluting  of  taps  and 
reamers,  Fig.  237,  which 
is  done  by  the  special 
cutters  already  referred 
to  in  Fig.  214.  It  will  be 
noticed  that  the  cutter 
should  be  set  in  such  a 
way  that  the  cutting  edge 
of  the  tap  or  reamer  will 
be  radial.  If  left  as  an 
obtuse  angle,  the  tool  will 
simply  scrape  and  not  cut;  while,  if  the  tooth  is  undercut  to  any 
extent  to  correct  this,  it  will  often  be  so  weakened  as  to  be  liable 

to  break. 

The  flutes  in  twist  drills 
and  in  spiral  fluted  reamers 
may  also  be  cut  between 
centers;  but,  if  the  cutter  is 
carried  directly  by  the  spin- 
dle, the  operation  requires  a 
universal  machine.  If  the 
cutter  be  carried  by  a  vertical 
or  sub-head  of  any  kind,  a 
plain  machine  will  answer  for 
the  purpose.  The  angle  to 
which  the  table  or  vertical 
head  must  be  set  for  spiral 
cutting,  Figs.  238  and  239, 
is  the  angle  between  the  axis 

Fig.  238.     Milling  Spirals  with  Table  at  Angle 

and  the  development  of  the 

spiral.    This  angle  can  be   closely  determined  by  the  following 
graphical  method : 


MACHINE  SHOP  WORK 


165 


Construct  a  right-angled  triangle  having  a  base  equal  to  the  axial  distance 
represented  by  one  full  turn  of  the  spiral  (this  is  the  lead  of  the  spiral),  and  a 
perpendicular  equal  to  the  circumference  of  the  work,  Fig.  240.  Draw  the 
hypothenuse  of  this  triangle.  If  the  construction  has  been  carefully  done,  the 


Fig.  239.     Cutting  Spiral  with  Milling  Machine 

Courtesy  of  Brown  and  Sharpe  Manufacturing  Company, 

Providence,  Rfiode  Island 

angle  between  the  base  and  the  hypothenuse  may  be  closely  determined  by  the 
use  of  a  protractor,  and  will  be  the  angle  to  which  the  table  or  head  must  be  set. 

This  angle  can  be  more  closely  and  quickly  determined  by  a 
very  simple  problem  in  plane  trigonometry — namely,  finding  the 
tangent  of  the  angle.  To  do  this,  divide  the  perpendicular  of  this 
triangle  by  its  base,  and  obtain  the  value  of  the  angle  from  a  table 
of  tangents. 

Spirals.  The  cutting  of  spirals  requires  another  operation  which 
differs  from  ordinary  work.  In  addition  to  the  angular  setting,  the 


'fingle    For    Table 
-SJxial    Lengtf~>    One    Turn- 


Fig.  240.     Graphical  Method  of  Determining  Angle  for  Cutting  Spirals 

work  must  be  rotated  in  order  to  produce  the  spiral,  as  well  as  fed 
forward  to  the  cutter.  This  rotation  of  the  work  must  be  positive, 
which  means  geared;  and  one  rotation  of  the  work  will,  of  course, 


166  MACHINE  SHOP  WORK 

equal  the  lead  of  the  spiral,  which  is  usually  expressed  as  one  turn  in 
n  inches.  After  cutting  one  spiral  groove,  the  work  is  turned  and 
indexed  the  same  as  in  plain  milling. 

Cams.  Both  open  and  closed  cams  can  be  readily  cut  on  a  plain 
milling  machine  by  the  use  of  the  cam-cutting  attachment,  Fig.  241, 
which  nearly  all  makers  are  able  to  furnish.  The  outline  of  the  cam 
is  first  laid  out  and  wrorked  down  by  hand  on  a  plain  disc,  or  male 
leader,  as  it  is  termed.  This  leader  and  a  suitable  blank  are  mounted, 


Fig.  241.     Cam-Cutting  Attachment  for  Milling  Machine 

Courtesy  of  Brown  and  Sharpe  Manufacturing  Company, 

Providence,  Rhode  Island 

with  their  outlines  coinciding,  on  the  spindle  of  the  cam-cutting 
attachment.  A  cam  roll  of  the  size  to  be  used  is  mounted  on  a 
stationary  roll  stud;  and  an  end  mill  of  the  same  diameter,  or  enough 
larger  for  clearance,  is  mounted  in  the  milling  machine  spindle 
directly  opposite  the  cam  roll.  The  spindle  of  the  cam-cutting 
attachment  is  mounted  on  a  carriage,  which,  by  means  of  a  weight 
over  a  pulley  at  the  end  of  the  milling  machine  table,  is  always  kept 
with  the  leader  in  contact  with  the  cam  roll.  A  worm  and  worm  gear 
are  used  for  rotating  the  attachment,  and  thus  the  spindle  approaches 


MACHINE  SHOP  WORK 


167 


or  recedes  from  the  cam  roll  according  to  the  shape  of  the  leader. 
When  cutting  closed  cams,  it  is  sometimes  desirable  to  use  the  hand- 
made male  leader  as  a  form  from  which  to  make  a  closed  or  female 
leader.  This  female  leader  will  surround  the  cam  roll  in  such  a  way 


Fig.  242.     Cutting  Spur  Gear  on  Milling  Machine 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  Island 

that,  even  if  the  weight  should  fail  to  act,  no  serious  damage  can  be 
done  to  the  blank.  The  cutting  of  face  cams  differs  from  the  above 
method  only  in  that  the  spindle  of  the  attachment  is  at  right  angles 
to  the  spindle  of  the  milling  machine,  instead  of  parallel  to  it.  The 
leader  and  cam  roll  are  used  in  the  same  manner  as  before. 


168 


MACHINE  SHOP  WORK 


Gears.  The  cutting  of  gears  of  all  descriptions  was  formerly? 
done  on  some  type  of  milling  machine,  although  now  each  type  or 
gear  may  have  its  special  and,  in  many  cases,  automatic  machine. 


Fig.  243.     Gear  Cutter  with  Divided  Head 

Forms  of  Cutters.  The  cutters  for  milling  spur  and  bevel  gears 
are  of  two  types,  producing  both  the  cycloidal  and  the  involute  tooth. 
For  each  pitch,  the  cycloidal  system  requires  twenty-four  cutters, 
while  eight  cutters  usually  suffice  for  the  involute  system.  These 

cutters  are  plainly  marked  with  the  style 
of  tooth,  pitch,  and  number  of  teeth  for 
which  they  are  suitable.  Some  cutters 
are  also  marked  with  the  full  depth  of  the 
tooth  expressed  in  thousandths  of  an 
inch,  Fig.  279.  The  gear  blanks,  having 
been  very  carefully  turned  as  to  outside 
diameter,  are  mounted  on  an  arbor  be- 
tween centers,  and  the  cutter  placed  so 
that  its  central  plane  passes  through,  and 
is  parallel  to,  the  axis  of  the  arbor. 
Clamp  the  saddle  in  this  position;  raise 
the  table  knee  until  the  cutter,  when 
rotating,  just  touches  the  outside  of  the 
blank.  Using  the  table  screw,  move  from 
under  the  cutter;  using  the  graduated  dial,  raise  the  knee  an  amount 
equal  to  the  whole  depth  of  the  gear  tooth.  With  the  exception  of 
the  indexing,  the  gear  blank  is.  now  ready  to  be  cut.  Fig.  242, 


Fig.  244.     Cutting  a  Bevel  Gear 


r 


MACHINE  SHOP  WORK 


169 


Use  of  Dividing  Head.  In  order  that  the  gear  may  be  accurately 
and  quickly  set  for  cutting  each  tooth,  a  dividing  head  is  used,  which 
is  shown  in  Fig.  243.  The  mandrel  upon  which  the  gear  blank  is 
mounted  is  held  by  the  centers  A  A,  and  firmly  dogged  to  the  face- 
plate B.  The  index  plate  C  is  geared  to  the  head  spindle  that  carries 


Fig.  245.     Robbing  Teeth  in  Worm  Wheel  • 

Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  Island 

the  faceplate  B;  the  index  plate  is  provided  with  a  number  of  holes. 
These  holes  are  arranged  in  circles,  each  circle  having  a  different 
number  of  holes,  and  these  holes  are  accurately  spaced  at  equal 
distances  apart.  The  arm  D  carries  a  stem  E,  having  a  knurled  head 
at  one  end  and  a  pin  at  the  other.  The  pin  is  held  in  one  of  the  holes 


170 


MACHINE  SHOP  WORK 


of  the  index  plate  by  a  spring.    The  arm  D  can  be  moved  to  any 
desired  position  relative  to  the  index  plate,  and  there  fastened. 

When  a  gear  is  to  be  cut,  the  arm  D  is  shifted  so  that  the  pin  is 
opposite  a  row  of  holes  the  number  of  which  is  the  same  as  the 
number  of  teeth  to  be  cut,  or  a  multiple  of  that  number.  Thus, 


Fig.  246.     Rack-Cutting  Attachment  on  Milling  Machine 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhlde  Island 

suppose  a  gear  with  45  teeth  is  to  be  made.  The  pin  may  be  set 
opposite  the  circle  of  90  holes.  Assuming  that  the  ratio  of  revolution 
between  D  and  B  is  40  to  1 ;  A  of  a  revolution  at  B  requires  If  of  a 
revolution  at  D.  The  pin  E  must,  therefore,  be  moved  Jf  of  90  holes, 
or  80  holes,  for  each  tooth  cut, 


MACHINE  SHOP  WORK  171 

Bevel  Gears.  Bevel  gears  are  held  on  a  taper-shank  arbor  in  the 
dividing  head,  which  is  swung  up  to  bring  the  bottom  of  the  tooth 
parallel  with  the  table,  Fig.  244.  As  all  parts  of  the  tooth  of  a  bevel 
gear  are  elements  of  a  cone,  it  is  evident  that  both  tke  tooth  and  the 
space  should  vanish  at  the  apex  of  the  cone.  No  solid  cutter,  there- 
fore, can  do  more  than  give  an  approximately  correct  shape  to  the 
tooth;  for  this  reason  two  cuts  are  made  in  order  more  nearly  to 
approach  the  desired  contour. 

Spiral  Gears.  Spiral  gears  are  cut  in  the  same  manner  as  any 
other  spiral — that  is,  by  using  the  angular  setting  of  the  head  or 
table  with  positive  rotation  of  the  work. 

Worm  Gears.  Worm  gears  can  be  hobbed  out  by  two  different 
methods.  A  common  method  is  to  gash  the  blank  with  a  stocking 
cutter;  then  mount  it  on  an  arbor  held  freely  between  centers,  so 
that  the  hob,  when  sunk  in  the  gashes,  will  rotate  the  blank.  The 
blank  is  raised  slowly  against  the  rotating  hob  until  the  hob  reaches 
the  proper  tooth  depth.  A  more  accurate  method  is  by  means  of  a 
train  of  gearing  to  rotate  the  blank  positively  at  a  speed  corresponding 
to  the  pitch  of  the  hob,  and  raise  the  rotating  blank  against  the 
rotating  hob  until  the  proper  tooth  depth  is  obtained.  This  method 
requires  no  preliminary  gashing,  Fig.  245. 

Rack  Cutting.  Rack  cutting  requires  a  special  attachment, 
Fig.  246,  so  that  the  cutter  spindle  may  be  carried  at  right  angles 
to  the  length  of  the  table. 

GRINDING  MACHINE 

Value  of  Grinding  as  Finishing  Process.  When  greater  accuracy 
than  that  obtainable  on  the  milling  machine  or  the  lathe  is  required, 
recourse  is  had  to  grinding.  This  operation  depends  upon  the  abrasive 
or  cutting  qualities  of  emery,  corundum,  and  carborundum.  With 
work  properly  held  to  a  solid  grinding  wheel,  it  is  not  difficult  to 
attain  great  accuracy.  By  means  of  the  grinding  machine,  parts 
may  be  economically  finished,  even  in  hardened  steel  that  could 
not  possibly  be  machined  on  such  shop  tools  as  the  lathe,  planer, 
or  shaper.  One  type  of  machine  used  for  this  purpose  is  shown 
in  Fig.  247.  With  such  a  machine,  round  surfaces  may  be 
ground  so  that  the  variation  from  the  nominal  diameter  is  less 
than  .0001  inch. 


172 


MACHINE  SHOP  WORK 


Features  of  Grinding  Process.  The  grinding  machine  illustrated 
in  Fig.  247  consists  of  a  strong  base  A,  upon  which  there  is  mounted 
a  headstock  B  and  a  tailstock  C,  similar  in  action  to  those  of  an 
ordinary  lathe.  rt  Back  of  these  is  an  emery  wheel  driven  by  a  separate 
belt.  The  principle  of  operation  for  round  surfaces,  is  that  the  part 
to  be  ground  is  put  upon  the  centers,  and  driven  exactly  as  in  the 
ordinary  lathe.  The  only  additional  precaution  to  be  taken  is  that 


\ 


Fig.  247.     Cylindrical-Grinding  Machine 

the  driving  apparatus  should  be  secure,  so  that  none  of  the  parts  are 
loose.  This  insures  a  continuous  motion  for  the  piece  with  no 
possibility  of  backlash.  The  piece  runs  toward  the  operator,  and 
the  emery  wheel  runs  in  the  same  direction.  The  two  surfaces  of 
wheel  and  work  in  contact  are  therefore  moving  in  opposite  directions. 
The  headstock  and  tailstock  are  mounted  upon  a  traveling  table 
Z),  which  moves  back  and  forth  in  the  same  manner  as  the  platen 
of  a  planer.  It  is  made  to  stop  automatically  at  each  end  of  the  stroke. 


MACHINE  SHOP  WORK  173 

When  work  is  being  done,  the  piece  is  centered,  with  its  axis 
parallel  to  the  line  of  travel  of  the  table.  With  the  piece  and  emery 
wheel  in  motion,  the  former  travels  to  and  fro  in  front  of  the  wheel. 
The  wheel  is  then  gradually  moved  forward  until  it  has  ground  the 
work  down  to  the  size  required. 

It  is  not  intended  that  large  amounts  of  metal  shall  be  removed 
by  this  machine.  Its  object  is  to  reduce  to  accurate  dimensions  the 
work  that  has  already  been  turned  in  the  lathe.  The  proper  method 
to  pursue  is  to  turn  the  piece  to  as  nearly  .the  required  diameter  as 
possible  in  the  lathe,  care  being  taken  that  it  is  left  a  trifle  large.  This 
may  be  .01  inch  on  each  2  inches  of  diameter.  The  surplus  metal  may 
then  be  removed  by  grinding.  In  the  machine  illustrated  in  Fig.  247, 
the  transverse  movement  of  the  wheel-stand  is  adjusted  by  a  hand- 
wheel  graduated  to  read  to  .001  inch  on  the  diameter  of  the  work. 
The  machine  is  also  provided  with  an  automatic  cross-feed,  which 
gives  a  range  of  advance  of  the  wheel  varying  from  .00025  inch  to 
.004  inch  at  each  reversal  of  the  table.  This  feed,  furthermore,  is 
so  arranged  that  it  can  be  automatically  released  at  any  point. 

Finishing  to  Size  after  Casehardening.  This  method  of  finish- 
ing is  also  used  for  pieces  that  have  been  casehardened.  Case- 
hardening  always  warps  the  metal  to  which  it  is  applied.  Grinding 
is  resorted  to  in  order  to  reduce  it  to  the  proper  shape.  An  example 
of  this  may  be  taken  in  the  method  used  in  the  manufacturing  of 
wrought-iron  locomotive  crank  pins.  The  pin  is  forged  and  turned 
to  as  near  the  working  size  as  possible.  It  is  then  casehardened  and 
ground  to  exact  alignment  and  dimensions. 

Grinding  is  also  used  for  truing  work  that  comes  from  the  lathe. 
The  lathe  does  not  turn  its  work  round,  owing  to  difference  in  the 
density  of  the  metal,  variation  in  the  cutting  speed,  dulling  of  the 
tool,  lost  motion  on  the  centers  and  in  the  spindle,  and  springing  of 
the  work  itself  due  to  pressure  of  the  tool.  The  grinding  machine 
remedies  this  to  a  great  extent — partly  because  only  a  very  slight 
pressure  is  brought  against  the  work;  partly  because  of  the  greater 
delicacy  of  adjustment  of  the  grinding  machine  as  compared  with 
the  lathe. 

The  method  of  grinding  flat  surfaces  is  practically  similar  to 
that  used  for  round.  The  work  is  bolted  to  the  table  and  moved  to 
and  fro  beneath  the  emery  wheel,  which  is  given  a  transverse  move- 


174 


MACHINE  SHOP  WORK 


merit  so  as  to  cover  the  whole  of  the  surface  to  be  operated  upon. 
The  surface  speed  of  the  wheel  may  range  from  4,500  to  6,000  feet 
per  minute. 

Action  of  Typical  Grinder.  Fig.  248  shows  a  typical  surface- 
grinding  machine  built  by  the  Brown  and  Sharpe  Manufacturing 
Company,  which  is  well  adapted  to  the  work  of  accurately  grinding 
flat  surfaces  up  to  quite  large  dimensions.  The  work  table  travels 


Fig.  248.     Surface-Grinding  Machine 

to  and  fro  in  a  manner  similar  to  that  of  a  planer,  and  carries  adjust- 
able reversing  dogs  which  may  be  set  to  limit  the  extent  or  position 
of  the  travel.  The  grinding  wheel  mechanism  is  supported  upon  a 
cross-rail  similar  to  that  in  a  planer  and  capable  of  vertical  adjust- 
ment on  the  arc  of  a  circle  whose  center  is  the  driving  shaft  supplying 
power  to  drive  the  grinding  wheel.  The  wheel  mechanism  carrying 
the  grinding  wheel  has  a  transverse,  automatic  feed  the  entire  width 
of  the  work  table. 


MACHINE  SHOP  WORK  175 

In  using  this  machine,  the  work  is  clamped  directly  to  the  table 
or  held  in  any  convenient  fixture,  as  a  milling  machine  or  planer  chuck 
or  vise.  In  strapping  work  to  the  table,  it  must  be  rigidly  held  in 
place;  but  it  is  not  necessary  to  clamp  it  down  as  tightly  as  on  the 
milling  machine  or  planer  table,  and  great  care  should  be  used  to 
avoid  springing,  warping,  or  other  distortion,  as  grinding  work  is 
expected  to  be  very  true  and  accurate;  in  fact,  this  is  its  chief  claim 
as  a  method  of  finishing  surfaces. 

To  avoid  distortion  from  overheating,  comparatively  thin  wheels 
are  generally  used,  particularly  if  the  piece  being  ground  is  thin  and 
light,  as  a  thin  casting  of  complicated  form. 

Selecting  the  Grinding  Wheel.  Grinding  wheels  are  made  with 
abrasives  as  coarse  as  No.  46,  and  as  fine  as  No.  150.  There  is  a 
great  difference  in  the  degree  of  hardness  of  a  wheel  due  to  the 
kind  of  bond,  or  adhesive  material,  with  which  the  abrasive  is  mixed 
in  forming  the  mass  of  which  the  wheel  is  composed.  As  to  the  fine- 
ness of  the  abrasive,  that  as  coarse  as  No.  46  is  suited  for  work  on 
rough  castings,  as  in  the  cleaning  room  of  a  foundry.  For  general 
work  in  shop  grinding,  the  roughing-off  will  be  best  done  with  a 
wheel  of  about  No.  60;  and  ordinary  finishing,  with  about  No.  90. 
For  very  fine  finishing,  the  wheel  may  be  much  finer. 

As  to  the  degree  of  hardness  of  a  wheel,  it  may  be  generally  said 
that  the  harder  the  material  to  be  ground  the  softer  should  be  the 
wheel.  There  are  several  degrees  of  hardness  made  by  the  manu- 
facturers, the  simplest  classification  being  Hard,  Medium,  and  Soft, 
designated  by  the  letters  H,  M,  and  S,  respectively.  All  letters  stand- 
ing before  M  in  the  alphabet,  refer  to  wheels  harder  than  medium; 
and  all  letters  after  M  refer  to  wheels  softer  than  medium. 

A  coarse  wheel  grinds  faster  than  a  fine  one,  but  leaves  deep 
scratches  in  the  work.  A  soft  wheel  may  be  made  of  a  much  finer 
grade  than  a  hard  one. 

A  soft  wheel  grinds  faster  than  a  hard  one,  but  it  is  apt  to  glaze 
over,  or  fill  up  with  particles,  if  used  on  a  soft  material. 

Lubrication.  To  increase  the  cutting  capacity  of  an  abrasive 
wheel,  to  prevent  it  from  glazing  over,  and  to  carry  off  the  heat 
generated  by  the  friction  of  the  wheel  on  the  work,  a  stream  of  water 
is  frequently  used,  arrangements  being  made  in  most  machines — 
particularly  in  those  for  grinding  tools  and  for  cylindrical  grinding — 


176 


MACHINE  SHOP  WORK 


TABLE  IX 
Speed  of  Grinding  Wheels 


DIAMETER 

MAXIMUM 

DIAMETER 

MAXIMUM 

DIAMETER 

MAXIMUM 

OF  WHEEL 

REVOLUTIONS 

OP  WHEEL 

REVOLUTIONS 

OF  WHEEL 

REVOLUTIONS 

(in.) 

PER  MlNU'.'E 

(in.) 

PER  MINUTE 

(in.) 

PER  MINUTE 

1 

19,000 

5 

4,400 

14 

1,580 

H 

12,500 

6 

3,700 

16 

1,380 

2 

19,000 

7 

3,160 

18 

1,230 

2£ 

8,800 

8 

2,770 

20 

1,100 

3 

7,400 

9 

2,460 

22 

1,000 

3^ 

6,300 

10 

2,210 

24 

920 

4 

5,500 

12 

1,850 

26 

850 

for  forcing  the  stream  upon  the  wheel  at  the  point  of  contact  with  the 
work  by  means  of  a  small  pump.  For  grinding  milling  cutters, 
reamers,  taps,  and  similar  tools,  water  is  not  used. 

Table  IX  gives  the  maximum  speeds  of  carborundum  wheels 
of  various  diameters. 

The  accuracy  of  grinding  renders  the  use  of  fine  measuring  tools 
a  necessity.  The  micrometer  caliper,  especially  with  the  vernier 
graduation,  is  best  suited  for  this  work. 

While  grinding  is  the  only  method  of  finishing  some  materials, 
such  as  hardened  tool  steel,  and  the  most  accurate  way  of  finishing 
any  kind  of  stock,  its  value  as  an  economical  method  has  only  lately 
been  recognized.  The  general  method  of  finishing  lathe  work  has 
been  to  take  a  roughing  cut  with  about  -^  inch  feed,  then  a  finishing 
cut  with  about  T!O~  inch  feed,  and  then  file  to  remove  the  tool  marks. 
In  the  majority  of  cases  it  is  more  economical,  as  well  as  more  accu- 
rate, to  take  a  roughing  cut  with  J  inch  feed  to  within  yj  inch  of  the 
size,  and  then  finish  by  grinding. 

In  some  cases  it  is  possible  to  get  excellent  results  by  grinding 
to  size  directly  from  the  bar  without  previous  turning.  (See  Part  V.) 

Lapping.  Lapping  Holes.  Lapping  is  a  term  applied  to  a 
particular  method  employed  in  the  grinding  out  of  holes.  The  lap 
consists  of  a  cylinder  of  soft  metal  run  rapidly  inside  the  hole  to  be 
lapped,  and  covered  with  emery  and  oil  at  the  same  time.  The 
surface  of  the  lap  should  invariably  be  of  soft  metal.  It  may  be  made 
of  copper,  or  it  may  be  an  iron  bar  with  a  covering  of  lead  or  tin.  It 
should  be  turned  slightly  tapering  at  each  end,  so  that  it  will  enter  the 
hole.  At  the  middle,  it  should  be  a  snug  fit. 


MACHINE  SHOP  WORK 


177 


The  end  of  the  bar  is  run  through  the  hole  and  set  on  the  lathe 
centers  with  a  dog  to  drive  it  like  an  ordinary  mandrel.  It  is  covered 
with  oil  and  sprinkled  with  emery.  The  lathe  is  then  run  at  a  high 
speed,  and  the  work  moved  to  and  fro  over  the  lap.  Light  pieces 
may  be  held  in  the  hand.  When  this  is  done,  care  should  be  taken 
to  turn  the  piece  so  that  the  grinding  may  be  even  over  the  whole 
circumference.  The  tendency,  when  holding  work  in  the  hand,  is 
to  allow  it  to  rest  upon  the  top  of  the  lap;  this  causes  the  grinding  to 
be  done  on  one  side  of  the  hole  unless  the  piece  is  frequently  turned. 
Laps  may  be  used  for 
grinding  holes  true  and 
parallel.  For  this  pur- 
pose the  work  should  be 
accurately  centered  with 
the  lap,  and  firmly  bolted 
to  the  lathe  carriage.  -The 
lap  is  then  run  at  a 
high  speed,  and  the  work 
moved  to  and  fro  over  it. 

Lapping  Flat  Sur- 
faces. Laps  are  some- 
times used  for  grinding 
flat  surfaces.  In  such 
cases  they  are  in  the 
form  of  discs.  They  are 
put  on  the  lathe  spindle 
in  the  place  of  the  face- 
plate. The  work  is  then 
pressed  against  the  disc.  As  the  outer  edge  of  the  disc  has  a 
higher  speed  in  feet  traveled  per  minute  than  those  portions  nearer 
the  center,  the  grinding  is  more  rapid  at  the  edges.  The  work  must, 
therefore,  be  constantly  turned  if  it  is  held  in  the  hand.  The  best 
way  is  to  clamp  it  firmly  on  the  lathe  carriage,  and  press  it  against 
the  lap  by  means  of  the  hand  feed. 

Disc  Grinder  for  Flat  Top  Work.  Laps  for  flat  surfaces  have 
grown  in  favor  so  rapidly  that  special  machines  called  disc  grinders 
have  been  made  to  do  this  work.  The  construction  of  the  disc  grinder 
can  be  so  readily  seen  from  the  illustration,  Fig.  249,  that  a  detailed 


Fig.  249.     Disc  Grinder 


178  MACHINE  SHOP  WORK 

description  is  not  necessary.  For  finishing  small  flat  surfaces,  espe- 
cially those  which  have  been  hardened,  this  machine  has  become  an 
important  factor  in  the  modern  shop. 

This  machine  is  arranged  for  using  ordinary  emery  wheels;  and 
the  grinding  is  done  on  the  side  of  the  wheel,  instead  of  on  its 
periphery;  hence  its  name.  The  table  rest  upon  which  the  work  is 
held  is  normally  horizontal,  but  is  adapted  to  be  set  at  any  required 
angle  when  the  work  is  of  such  a  form  as  to  require  this  adjustment. 

The  usual  difficulty  experienced  in  this  method  of  using  an 
emery  wheel  is  the  liability  of  the  disc  to  glaze  over,  and,  as  a  result, 
require  frequent  turning  off  to  present  a  good  cutting  surface.  Many 
attempts  were  made  to  replace  the  solid  emery  wheel  with  a  cast-iron 
disc  covered  with  emery  cloth;  but  the  same  difficulty  was  found  in 
its  use.  The  experiment  was  tried,  of  cutting  slight  grooves  in  various 
directions,  generally  concentric  or  radial,  in  the  face  of  the  cast-iron 
disc.  Its  usefulness  was  improved;  but  the  problem  was  not  solved 
until  a  single  spiral  groove  was  cut,  starting  near  the  center  and 
running  gradually  outward.  By  this  means  the  tendency  to  glaze  is 
broken  up  in  a  continually  progressive  manner  that  effectually  pre- 
vents this  trouble. 

Machines  similar  to  the  one  shown  in  Fig.  249  are  built  with 
double  heads  so  that  two  discs  are  placed  facing  each  other,  one  of 
them  being  capable  of  adjustment  so  that  flat  pieces  of  work  can  be 
ground  on  both  sides  simultaneously.  Machines  of  this  kind  are 
adapted  to  a  considerable  range  of  very  useful  work. 

LAYING  OUT  WORK 

Laying  out  work  is  one  of  the  most  important  details  of  machine 
shop  practice.  Ordinarily  all  work  is  laid  out.  The  exceptions  are 
where  certain  pieces  are  worked  from  templets,  and  in  these  cases 
the  templet  is  laid  out  from  certain  points  on  the  casting,  forging, 
punching,  or  whatever  is  used  for  the  work  in  hand. 

Centering  Round  Bars.  The  simplest  form  of  laying  out  work  is 
to  be  found  in  the  centering  of  round  bars  that  are  to  be  turned  in 
the  lathe.  In  this  case  the  end  of  the  piece  is  chalked.  Use  a  pair 
of  hermaphrodite  calipers;  set  the  points  A  and  B  so  that  their 
distance  apart  is  a  little  more  than  the  radius  of  the  piece.  Place  the 
caliper  leg  at  three  points  on  the  circumference,  A,  B,  and  C, 


MACHINE  SHOP  WORK  179 

Fig.  250;  and  describe  from  each  the  arcs  of  circles  A'  A' ,  Bf  Bf ,  and 
C"C",  respectively.  Then,  with  the  prickpunch,  mark  the  point 
indicated  by  the  small  circle  in  the  center.  This  will  be  the  center. 
To  test  its  accuracy,  place  the  divider  leg  in  the  prickpunch  mark, 
and  see  if  the  caliper  leg  will  just  touch  the  bar  over  its  whole  surface. 

Before  drilling,  the  center  should  be  emphasized  with  a  center 
punch. 

The  center  square  may  be  used  for  the  operation  of  locating 
centers  in  round  stock,  as  the  center  can  be  easily  located  at  the 
intersection  of  two  diameters  drawn  nearly  at  right  angles.  In  some 
cases.it  is  better  to  lay  the  shaft  in  V-blocks  on  a  plate  and  use  the 
surface  gage,  drawing  at  least  two  lines 
through  the  center  of  the  piece. 

It  is  often  necessary  to  cover  the 
surface  of  the  work  where  lines  must  be 
visible,  with  chalk,  white  lead,  or  cop- 
peras, before  any  laying  out  can  be  done; 
but  in  cases  of  this  kind  it  is  usual  to 
mark  directly  upon  the  end  of  the  bar. 
Before  drilling,  the  center  should  be 
emphasized  with  a  center  punch.  rig.  250.  Centering  Round  Bar  to 

,  .  PIT  1111  be  Turned  in  Lathe 

The  locations  tor  holes  should  be 

at  the  intersection  of  lines  in  order  to  be  plain.  After  marking 
the  center  with  a  prickpunch,  take  a  pair  of  dividers  and  describe 
a  circle  on  the  prepared  surface  concentric  with  the  center  already 
located.  This  circle  should  be  about  the  diameter  of  the  hole  to  be 
drilled;  and  in  many  good  shops,  it  is  the  custom  to  draw  another 
circle  concentric  with  the  first  and  about  TQ  mcn  larger  in  diam- 
eter. This  outer  circle  is  called  the  reference  circle,  and  is  for 
the  benefit  of  the  inspector  when  it  becomes  necessary  to  place 
the  responsibility  for  a  misplaced  hole.  These  circles  may  be 
marked  with  at  least  four  prickpunch  marks,  as  shown  in 
Fig.  178,  Part  II,  in  order  to  indicate  the  position  of  the  circle 
in  case  of  the  obliteration  of  the  line.  The  center  is  then  deep- 
ened by  the  center  punch,  and  the  hole  drilled.  In  laying  out 
centers  upon  rough  castings,  the  first  thing  to  do  is  to  snag  the 
work — that  is,  remove  the  ridges  of  the  casting  caused  by  the 
pattern  being  made  in  two  or  more  parts.  For  small  castings  a 


180 


MACHINE  SHOP  WORK 


Fig.  251.     Laying  Out  Valve  Seats 


coarse  file  is  generally  used,  while  for  large  work  the  cold  chisel  is 

used.    In  many  shops  the  cold  chisel  is  operated  by  compressed  air. 

Lay  out  for  Planer  and  Milling  Machine.    In  laying  out  the  work 

for  the  planer  and  milling  machine,  great  care  must  be  exercised. 

It   is  necessary  that   there 

c- 1  **  B       i_  should    be   a   base   line    to 

which  the  lines  may  be  re- 
ferred. It  depends  on  the 
character  of  the  work  as  to 
how  this  should  be  done. 

Sometimes  it  is  quite  sufficient  to  lay  off  the  base  line  parallel  to  one 
side  of  the  casting  or  forging.  If  the  side  thus  used  is  to  be  finished, 
then  the  base  line  should  be  located  at  the  proper  distance  from  it  to 
allow  for  the  finishing.  The  amount  required  varies  with  the  char- 
acter of  the  casting  or  forging ;  this  has  been  fully  explained.  Usually 
there  is  some  outline  of  the  rough  piece  that  will  serve  as  a  guide. 

As  an  example  of 
the  laying-out  of  work, 
take  the  valve  and  steam- 
chest  seats  shown  in 
Figs.  251  and  252.  The 
work  is  to  be  machined 
on  a  planer.  The  cylin- 
der has  probably  been 
bored.  It  is  then  placed 
on  the  planer,  and  so  set 
that  the  center  line 
through  the  cylinder  is 
parallel  to  the  platen  of 
the  planer.  The  first 
machine  work  to  be  done 
is  the  taking-off  of  the 
roughing  cut  from  the 

face  A.  This  face  is  to  be  planed  down  to  a  certain  height  above  the 
cylinder  center;  this  height  may  be  marked  on  the  edge  of  the  valve- 
seat  by  the  prickpunch  mark  B.  If  the  surface  C  is  to  be  planed  at 
the  same  time,  its  height  is  indicated  by  the  prickpunch  mark  D. 
These  points  may  be  located  by  means  of  the  surface  gage.  Set  the 


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V    1    p  T  R 

A, 

i 

v 

'* 

J 

p 

•L- 

J_ 

H 

j, 

(DV 
i 

d)v 

C 

5  M   \    O 

S  G 

C 

i 

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0  0  j  Q_  _  _£X 

Fig.  252. 


F 

Layout  of  Steam  Ports 


MACHINE  SHOP  WORK  181 

gage  on  the  platen,  and  elevate  the  point  to  the  proper  height. 
Move  it  so  that  it  will  touch  the  side  of  the  casting  at  the  proper 
point,  and  make  the  marks  B  and  D  accordingly.  When  the  surfaces 
A  and  C  have  received  the  roughing  cut,  the  plan  may  be  laid  off 
as  in  Fig.  252.  WTith  a  square  having  a  suitable  length  of  blade, 
locate  the  points  G  and  //  directly  over  the  center  of  the  cylinder. 
Cover  the  surfaces  A  and  C  with  chalk  where  lines  are  to  be  drawn. 
Draw  the  lines  7,  J,  K,  and  L  on  the  surface  A,  between  G  and  //. 
Through  the  center  of  the  side  of  the  exhaust  port,  draw  the  lines 
E  and  F  at  right  angles  to  GH.  This  is  done  with  a  scriber.  Lay 
off  half  the  width  of  the  exhaust  port  on  either  side  of  E  and  F, 
and  draw  the  lines  M  N  and  OP  parallel  to  E  and  F.  In  like  manner, 
draw  the  lines  QR  and  S  T  for  the  limits  of  the  steam  ports.  All  of 
these  lines  are  to  be  emphasized  by  the  use  of  prickpunch  marks 
as  indicated. 

If  the  sides  of  the  valve-seat  are  to  be  finished,  the  line  to  which 
the  metal  is  to  be  cut  is  indicated  in  the  same  manner.  Finally,  the 
holes  VVV,  etc.,  for  the  holding-down  studs  of  the  steam  chest,  are 
to  be  laid  out.  The  center  lines  are  first  drawn ;  then  the  centers  of 
the  holes  are  marked,  after  which  the  circles  for  the  holes  are  drawn 
as  already  described. 

Layout  for  Lathe.  Wrork  is  rarely  laid  out  for  the  lathe.  It  is 
not  necessary  that  it  should  always  be  done  for  the  planer.  Laying 
out  is  employed  where  accuracy  is  essential,  and  where  it  is  possible 
to  secure  the  proper  dimensions,  with  the  piece  to  be  operated  upon 
in  position  on  the  machine. 

The  man  who  has  charge  of  the  work  of  laying  out  should  have 
some  knowledge  of  the  elementary  principles  of  geometry;  he  should 
also  have  some  knowledge  of  drawing,  and  should,  of  course,  be  able 
to  read  drawings. 

General  Suggestions.  A  few  general  suggestions  may  be  given 
regarding  work  to  be  finished  in  the  vise  on  either  the  planer,  shaper, 
or  milling  machine,  where  several  faces  are  to  be  finished  at  right 
angles  to  one  another.  Referring  to  the  rectangular  block  of  Fig.  253, 
the  block  is  first  placed  in  the  vise  with  the  face  MNOP  down, 
and  the  face  MADP  against  the  fixed  jaw.  The  face  A  BCD  is  then 
machined,  and  the  work  turned  so  that  A  BCD  is  against  the  fixed 
jaw,  and  MAVP  down.  With  the,  block  in,  this  position,  NBCO 


182  MACHINE  SHOP  WORK 

is  worked,  making  NBCO  at  right  angles  to  A  BCD.  With  A  BCD 
still  against  the  fixed  jaw,  and  NBCO  down,  surface  MADP  is 
next  worked.  This  brings  two  edges  at  right  angles  to  the  same  side 
and  parallel  to  each  other.  Then,  placing  A  BCD  down  and  either 
MADPor  NBCO  against  the  fixed  jaw,  surface  MNO  Pis  generated 
parallel  to  A  BCD.  This  leaves  the  ends  to  be  finished.  The  vise  is 
swung  so  that  the  fixed  jaw  is  at  right  angles  to  the  line  of  motion 
of  the  tool;  and  on  the  planer  and  shaper  they  are  finished  by  using 
the  vertical  feed.  In  the  two  last-named  tools,  the  tool  holder  is 
swung  so  that  the  tool  will  clear  the  work  easily  on  the  return  stroke. 
In  working  cast  iron  it  is  well  to  chamfer  the  edges  with  a  file. 
If  this  is  not  done,  the  metal  will  break  off  when  the  tool  reaches  the 

end  of  the  cut,  leaving  a 
ragged  edge.  The  depth  of 
the  chamfer  depends  on  the 
amount  of  metal  to  be  re- 
moved. 

Fitting.     Fitting    is    the 
term  generally  applied  to  the 

Block  to  be  Finished  hand    work    necessary    in 

assembling  machinery  after  all 

the  machine  work  has  been  done.  Filing,  either  in  the  vise  or 
lathe,  and  scraping,  are  the .  operations  usually  required,  although 
the  hammer  and  chisel  are  sometimes  used.  As  hand  work  costs 
much  more  than  machine  work,  the  machining  is  .done  as  closely  as 
possible  to  make  the  hand  work  a  very  small  item. 

SHOP  SUGGESTIONS 

In  the  regular  work  of  any  shop,  occasions  are  constantly  arising 
for  the  determination  of  the  best  method  of  doing  work.  The  success 
with  which  the  desired  end  is  attained  depends  upon  the  skill  and 
judgment  of  the  man  in  charge.  While  it  is  impossible  in  a  limited 
space  to  give  instructions  regarding  every  possible  emergency  that 
may  arise,  a  few  suggestions  regarding  shop  practice  will  be  valuable. 

Peening.  Peening  consists  in  stretching  the  metal  on  one  side  of 
a  piece  of  work  in  order  to  alter  its  shape.  There  is  a  wide  difference 
between  peening  and  bending.  For  example,  suppose  the  curved  or 
warped  piece  in  Fig.  254  is  to^  be  straightened.  If  it  were  to  be 


MACHINE  SHOP  WORK  183 

bent  until  it  were  straight,  it  would  be  placed  on  the  block  A  with 
the  concave  surface  down,  as  shown  by  the  dotted  lines.  It  could 
then  be  struck  by  the  hammer  and  driven  down  past  the  line  of 
support,  and  strained  so  that  it  would  remain  approximately  straight. 
Such  a  method  of  straightening  could  not  be  applied  to  a  piece  of 
complicated  outlines.  It  would  remain  wavy.  In  peening  to  trueness 
such  a  piece  as  shown  in  Fig.  254,  it  is  laid  on  an  anvil  with  the  convex 
surface  down.  It  is  then  struck  with  the  peen  of  the  hammer  on  the 
concave  side.  The  blow  must  be  quick  and  sharp.  The  result  is 
that  the  metal  is  stretched  at  the  point  where  the  blow  is  struck. 
By  working  successively  over  the  whole  surface,  the  concave  side  is 
stretched  so  that  it  is  equal,  in  its  dimensions,  to  the  convex  side. 
The  piece  then  becomes  straight, 
and  will  so  remain.  A  skilful 
use  of  the  hammer  will  straighten 
almost  any  piece  of  thin  metal. 

Drilling  Hard  Metals.    It  is 
sometimes  desirable  to  drill  a  hole     .____^, 
in  very  hard  metal.    To  do' this    ^ 
the  drill  must  be  made  very  hard; 

it  must  be  run  at  a  very  slow  speed;  it  must  be  forced  against  the 
work  as  hard  as  possible  without  breaking  the  point;  and  it  must  be 
provided  with  an  abundant  supply  of  oil.  For  excessive  hardening 
of  a  drill,  it  may  be  heated  to  a  dull  red  heat,  preferably  in  a  charcoal 
fire,  and  quenched  in  mercury  instead  of  water,  in  order  to  make 
the  cooling  more  rapid.  It  will  also  assist  in  the  operation,  if  the 
surface  of  the  metal  to  be  drilled  is  nicked  with  a  cold  chisel  before 
work  is  begun.  In  some  cases  turpentine,  in  place  of  oil,  may  be  used 
with  beneficial  results. 

Thin  chilled  cast  iron  may  be  softened  by  placing  a  small 
piece  of  sulphur  on  the  place  where  a  hole  is  desired,  and  then  heating 
slowly  to  a  dull  red. 

Glass  may  also  be  drilled.  .  There  are  two  methods:  one  is  to 
use  a  flat  drill  moistened  with  camphor  and  turpentine;  and  the 
other  is  to  use  a  copper  tube  with  No.  60  emery  or  carborundum  and 
oil.  In  the  last  method,  drill  half-way  through,  reverse,  and  drill 
to  meet,  removing  the  fin  at  the  center  with  a  round  file  wet  with 
water  or  turpentine. 


184  MACHINE  SHOP  WORK 

Grinding  Valves.  This  is  a  kind  of  grinding  that  is  usually 
done  by  hand.  It  consists  in  fitting  a  valve  and  its  seat  so  that 
they  are  in  metallic  contact.  In  its  results,  it  is  the  same  as  scraping. 
The  process  is  very  simple.  The  valve  is  coated  with  oil,  and  some 
fine  emery  sprinkled  over  it.  It  is  then  put  on  the  seat  and  worked 
back  and  forth  or  revolved.  The  emery  serves  to  grind  off  the  high 
surfaces  of  both  valve  and  seat.  After  grinding  for  #,  time,  remove 
the  valve,  and  wipe  both  surfaces  clean.  The  metal  on  each  will 
show  where  they  have  been  in  contact.  When  these  indications 
appear  over  the  whole  of  the  surface,  or  in  a  continuous  ring  about 
the  seat  of  a  circular  valve,  the  work  is  completed. 

Generating  Surface  Plates.  In  this  operation  it  is  necessary  to 
work  with  three  at  the  same  time.  For  the  sake  of  making  the 
explanation  clear,  they  will  be  called  A,  B,  and  C.  After  the  plates 
have  been  planed,  a  straightedge  should  be  laid  on  each.  A  straight- 
edge is  merely  a  piece  of  flat  steel  having  one  or  more  edges  true  and 
straight.  Set  the  straightedge  on  the  plates  in  all  directions.  If  it 
touches  over  its  whole  length  in  all  positions,  then  the  plates  are 
ready  for  scraping.  If  it  touches  at  the  edges  of  the  plate  and  is  clear 
in  the  center,  the  former  are  high  and  should  be  filed  down.  If  it 
touches  in  the  center  and  rocks  to  and  fro,  the  plate  is  convex  and 
the  center  must  be  filed  down.  After  the  plates  have  been  filed  to 
trueness  as  far  as  trueness  can  be  indicated  by  the  straightedge, 
they  are  ready  for  scraping. 

Now  take  plates  A  and  B  and  place  them  face  to  face.  Strike 
a  blow  on  the  upp  r  one,  and  it  will  cause  a  jarring  sound  to  be 
heard.  This  shows  that  the  two  are  not  in  perfect  contact.  Smear 
the  surface  of  plate  A  with  a  thin  mixture  of  red  lead  and  oil.  Cover 
the  surface  evenly  and  thinly.  Then  rub  the  two  plates  together, 
and  where  the  red  lead  comes  off  onto  the  surface  of  plate  B,  the 
two  come  in  contact.  Take  the  scraper  and  scrape  off  a  little  of 
the  metal  from  each  of  the  plates  where  they  have  been  in  contact. 
Wipe  off  plate  B;  and  again  smearing  plate  A,  proceed  as  before. 
Continue  this  process  until  the  two  surfaces  are  in  contact  over  their 
whole  areas.  This  does  not  prove,  however,  that  they  are  flat. 
They  may  be  in  contact,  as  required,  if  A  is  convex  and  B  is  concave. 
To  test  this,  the  third  plate  is  necessary.  Smear  plate  B  with  red 
lead,  and  scrape  C  to  fit  it.  Do  not  touch  A,  It  is  evident  that  A 


MACHINE  SHOP  WORK 


185 


and  C  will  then  be  alike.  Bring  them  together.  If  they  are  both 
convex  they  will  roll  over  each  other.  If  they  are  concave  they  will 
bear  at  their  edges,  and  not  touch  in  the  center.  They  will  appear 
to  be  out  of  true  by  twice  the  actual  amount.  Scrape  off  the 
contact  points  of  A  and  C.  Remove  as  nearly  as  possible  the  same 
amount  of  metal  from  each.  When  these  two  plates  have  been 
brought  so  as  to  be  in  contact  over  their  whole  areas,  lay  plate 
aside,  and  scrape  B  until  it  fits  C,  but  do  not  touch  A.  Try  A  and 
B  together.  If  they  do  not  touch  over  their  whole  areas,  treat  them 
as  before  described  for  A  and  C.  Then  introduce  C  again.  Continue 
this  alternating  process  until  each  of  the  three  plates  forms  a  bearing 
over  the  whole  of  the  surface  of 
each  of  the  other  two. 

During  the  latter  part  of  the 
process,  use  alcohol  instead  of  red 
lead.  This  will  leave  clean,  bright 
spots  at  the  points  of  contact. 

Fitting  Brasses.  This  is  a 
piece  of  work  now  usually  done  on 
a  machine,  but  sometimes  done  by 
hand.  Brasses  which  are  to  be 
used  for  connecting  rods,  and 
which  are  made  in  two  pieces,  as 
shown  in  Fig.  255,  have  a  tendency  to  warp  after  the  machine  work  has 
been  done  on  them.  The  difficulty  arises  from  their  closing  along  the 
diameter  A.  Thus,  if  the  brass  is  finished,  and  the  hole  bored  out 
to  the  proper  diameter,  and  is  then  cut  apart  on  the  line  CD,  it  will  be 
found,  shortly  afterward,  that  the  diameter  A  is  less  than  the 
diameter  B.  It  may  therefore  be  necessary  to  bore  the  hole  somewhat 
larger  than  the  working  diameter.  The  kerf  made  by  the  saw  will 
usually  allow  the  parts  to  be  drawn  together  along  the  diameter  B, 
so  that  it  will  more  than  make  up  the  shrinkage  at  A .  The  hole  can 
then  be  scraped  to  fit  the  pin.  The  brasses  should  always  be  keyed 
solidly,  metal  to  metal.  This  avoids  a  wear  of  the  sides  and  edges  of 
the  metal,  due  to  the  thrust  of  the  rod. 

Joints.  Where  a  gas  or  liquid  is  to  be  retained  in  a  pipe  or 
other  vessel  without  leakage,  a  tight  joint  is  necessary.  The  method 
of  grinding  valves  to  their  seats  has  already  been  explained.  In  that 


Fig.  255.     Coniiecting-Rod  Brasses 


186  MACHINE  SHOP  WORK 

case,  it  was  shown  that  a  metallic  contact  between  the  valve  and  its 
seat  is  all  that  is  required  in  order  to  make  it  a  tight  joint.  Two 
surfaces  that  have  been  scraped  to  fit  will  also  accomplish  the  same 
purpose.  This  is  frequently  too  expensive  an  operation  to  be  per- 
formed, especially  on  rough  work.  In  such  places  a  softer  material 
may  be  interposed  between  the  two  surfaces.  Where  the  joint  is  to 
be  a  permanent  one  and  is  not  to  be  taken  down,  the  red  lead  joint  is 
usually  employed.  This  consists  in  the  use  of  a  mixture  of  red  and 
white  lead  between  the  joints.  To  ordinary  white  lead  ground  in 
oil,  add  enough  dry  red  lead  to  make  a  paste  that  can  be  spread 
without  sticking  to  the  blade  with  which  it  is  applied.  After  the 
mixture  has  been  made,  it  will  be  improved  by  pounding  it  well  with 
the  hammer.  It  may  then  be  laid  between  the  two  pieces  of  metal 
forming  the  sides  of  the  joint,  and  the  latter  be  drawn  together. 
Red  lead  joints  are  extensively  used  in  pipe-fitting.  The  red  lead 
has  a  tendency  to  rust  the  iron  with  which  it  is  in  contact,  and  thus 
forms  a  very  tight  connection  between  the  two  pieces.  Where 
provision  is  to  be  made  for  taking  down  the  joint  at  a  future  time,  it 
is  better  to  use  a  graphite  paste  made  for  the  purpose.  This  does  not 
rust  the  metal  and  it  forms  a  perfectly  tight  joint,  which  may  be 
taken  down  without  difficulty  at  any  time. 

Joints  that  are  subject  to  occasional  disconnecting  can  be  best 
held  by  a  disc  of  rubber  packing.  The  latter  is  cut  to  fit  the  flanges 
between  which  the  joint  is  to  be  made,  and  they  are  then  drawn 
tightly  together. 

Joints  that  are  to  be  frequently  taken  down  are  usually  packed 
with  a  piece  of  copper  wire.  Such  a  place  is  the  joint  between  the 
steam  chest  and  cylinder  of  a  locomotive  engine.  A  groove  is  cut  in 
the  two  surfaces,  and  a  copper  wire  is  laid  therein.  This  wire  should 
be  about  J  inch  in  diameter.  Its  size,  however,  depends  upon  the 
joint  to  be  packed.  The  ends  of  the  wire  are  soldered  together  so 
that  no  leakage  may  occur  past  the  ends. 

Another  form  of  joint  is  the  rust  joint.  This  is  always  per- 
manent in  character.  The  making  of  such  a  joint  consists  in  rusting 
the  two  surfaces  together.  The  following  are  the  proportions  by 
weight  of  the  rusting  material:  100  parts  of  iron  turnings,  1  part  of 
sal  ammoniac,  and  J  part  of  sulphur.  The  setting  of  the  joint  can 
be  hastened  by  increasing  the  amount  of  sal  ammoniac  from  15  to 


MACHINE  SHOP  WORK  187 

25  per  cent.  Mix  the  ingredients  thoroughly,  and  just  cover  them 
with  water. 

Fluting  Rollers.  Where  feed  rollers  such  as  those  used  in  wood- 
working machinery  are  to  be  turned  and  fluted,  the  turning  should 
always  be  done  first.  This  insures  a  continuous  surface  for  the 
cutting  tool.  Where  old  rollers  are  to  be  re-turned  and  fluted,  the 
same  rule  applies.  The  fluted  surface  may  be  turned  to  size.  The 
lathe  tool  will  break  the  edge  of  the  ribs  away;  but  when  the  fluting 
is  done,  these  edges  are  again  made  smooth.  The  fluting  can  be  done 
on  a  planer,  with  a  round-nosed  tool.  The  roller  should  be  held  on 
centers  and  clamped  so  that  each  groove  may  be  presented  to  the 
tool  in  succession.  A  planer  center,  as  illustrated  in  Fig.  190,  Part  II, 
affords  a  convenient  method  of  holding  and  turning  the  work. 

Scale.  Whenever  a  piece  of  cast  iron  is  to  be  turned,  the  point 
of  the  tool  should  always  be  made  to  work  beneath  the  scale.  The 
scale  is  the  hard  outer  shell  that  covers  all  cast  iron  as  it  comes  from 
the  foundry.  It  is  very  hard  and  brittle.  If  the  edge  of  the  tool  is 
made  to  work  in  or  against  it,  that  edge  will  soon  be  dulled.  If  it  is 
beneath  it,  the  raising  of  the  chip  cracks  and  removes  the  scale. 

Pickling.  Where  castings  are  to  be  worked,  either  in  the  lathe 
or  planer,  to  dimensions  only  a  little  less  than  those  when  rough,  they 
should  be  pickled.  This  consists  in  washing  them  with  a  solution 
of  sulphuric  acid  and  water.  The  castings  may  be  either  submerged 
in  or  swabbed  with  the  solution.  The  effect  of  pickling  is  to  cause 
the  scale  to  drop  off  in  flakes,  leaving  the  metal  bare,  unprotected,  and 
rusty.  The  casting  should  then  be  washed  with  a  sal  soda  solution. 
A  good  pickling  solution  for  this  work  is  to  use  1  part  of  commercial 
sulphuric  acid  in  10  parts  of  water. 

Cold  Chisels.  It  is  well  to  use  a  coarser  grade  of  steel  for  cold 
chisels  than  for  lathe  or  planer  tools.  A  coarse-grained  metal  is 
preferable  because  the  continual  hammering  in  use  and  redressing 
will  gradually  modify  the  granular  structure  until  it  is  microscopic 
in  texture.  In  dressing,  it  should  never  be  heated  above  a  cherry 
red,  and  the  temper  should  be  drawn  well  down  so  that  the  soft  metal 
backs  up  the  edge.  A  capacity  to  receive  a  multitude  of  grindings 
is  not  what  is  wanted.  The  tool  must  be  able  to  endure  the  severe 
service  for  which  it  is  intended.  It  must  cut  into  a  distorted  mass  of 
metal,  where  every  blow  gives  it  a  shock  tending  to  form  a  new 


188  MACHINE  SHOP  WORK 

arrangement  of  its  particles.  It  never  receives  the  steady  pressure 
of  the  lathe  tool;  hence  its  powers  of  endurance  must  be  greater. 

Lining  Shafting.  In  equipping  a  shop,  the  first  work  of  the 
machinist  is  the  erection  of  the  shafting.  The  main  line  should  be 
the  first  laid  out;  and  the  engine,  together  with  the  jack  and  counter- 
shafting,  must  be  located  from  it.  After  placing  the  hangers  as 
nearly  as  possible  in  a  horizontal  line,  the  shafting  should  be  placed 
in  the  boxes  and  attached  to  the  hangers.  For  lining  the  shaft,  a 
level  and'a  fine  grass  or  silk  line  are  indispensable.  The  line  is  tightly 
drawn,  horizontally,  a  short  distance  from  the  position  the  shaft  is 
intended  to  occupy,  and  the  distance  from  the  surface  of  the  shaft 

to  the  line  is  measured  and 
made  equal  near  each  hanger 
stick I  by  a  stick  such  as  shown  in 

Fig.  250.     GaSe  for  Parallel  Lining  of  Shafting  ^  1S'  *«"• 

The  level  is  used  to 

make  the  shaft  horizontal;  and,  if  the  hangers  are  adjustable  in  two 
planes,  the  operation  is  quite  rapid. 

When  other  shafting  is  to  be  erected  parallel  to  the  first,  if  the 
distance  does  not  exceed  twelve  or  fifteen  feet,  a  long  stick  may  be 
used  by  driving  a  nail  into  the  end  of  the  stick  to  allow  some  adjust- 
ment. The  level  is  used  as  before. 

When  the  distance  is  great,  or  obstacles  prevent  the  use  of  the 
stick  as  suggested,  a  line  may  be  drawn  on  the  floor  of  the  shop  by 
dropping  a  plumb  line  from  near  the  ends  of  the  first  shaft  and 
connecting  the  points  located.  Another  line,  directly  under  the 
desired  location,  may  be  drawn  by  direct  measurement,  and  the 
second  shaft  erected  by  dropping  a  plumb  line  to  this  second  floor 
line  near  the  ends  of  the  second  shaft.  This  method  may  be  employed, 
with  such  variations  as  the  case  may  demand,  even  though  a  floor  or 
wall  be  between  the  locations. 

In  leveling  up  long  lines,  or  around  machines,  or  through  walls, 
the  hydrostatic  level  is  a  most  convenient  tool.  It  consists  of  two 
graduated  glass  tubes  set  in  suitable  bases  and  connected  by  a 
rubber  tube.  When  the  rubber  tube  is  filled  with  water,  and  the 
glass  tubes  placed  vertically  on  the  shaft,  the  fluid  should  stand  at 
the  same  graduation  in  each  glass.  These  levels  are  made  with  self- 
acting  valves  to  prevent  the  escape  of  the  fluid. 


MACHINE  SHOP  WORK 


189 


When  pulleys  or  hangers  make  the  direct  application  of  a  level 
to  the  shaft  impracticable,  leveling  hooks,  in  connection  with  a 
wooden  straightedge,  as  shown  in  Fig.  257,  are  very  convenient. 
These  may  be  made  of  wood  or  metal,  and  of  lengths  suitable  to  the 
case  in  hand. 

Machine  Setting.  After  the  shafting  is  erected,  comes  the 
setting  of  machines.  The  countershafts  are  first  erected  parallel  to 
the  main  line,  and  with  due  regard  to  the  location  of  the  machine. 
The  machine  is  then  placed,  writh  its  driving  shaft  parallel  to  the 
counter,  by  use  of  the  plumb  line;  and  the  platen,  table,  or  other 
horizontal  surface  carefully  leveled,  in  two  planes,  by  wedging  up 


Fig.  257.     Method  of  Using  Level  for  Lining  Shafting 

the  machine  with  common  shingles.    The  machine  is  then  secured 
to  the  floor  by  lag  screws. 

When  the  machines  are  very  heavy,  and  stone  or  masonry 
foundations  are  necessary,  anchor  bolts  are  built  into  the  foundation 
at  suitable  points,  or  holes  drilled  for  expansion  bolts.  The  machine 
is  then  lined  and  leveled  as  already  suggested.  The  bottom  of  the 
machine,  however,  is  usually  a  rough  casting;  the  top  of  the  stone 
foundation  is  still  rougher;  and,  as  the  wedges  are  likely  to  slip  out 
under  the  jarring  of  the  machine,  a  permanent  support  must  be 
provided.  This  may  be  done  by  pouring  melted  sulphur  beneath 
the  bed.  To  do  this,  build  a  dam  of  clay  or  sand  all  around  the  bed 
and  about  2  inches  high.  Melt  ordinary  stick  sulphur  or  brimstone 
in  ladles,  and  pour  in  at  several  points  at  once.  Keep  the  space 
flooded  until  the  dam  is  well  filled,  and  allow  it  to  harden.  This  will 


190  MACHINE  SHOP  WORK 

occur  very  quickly,  after  which  the  dam  may  be  removed  and  the 
sulphur  cut  away  from  the  edge  of  the  machine.  Care  must  be 
taken  that  the  temperature  of  the  sulphur  is  as  high  as  possible 
before  pouring.  Unless  this  is  done,  it  will  cool  and  set  before  reach- 
ing the  inmost  recesses  beneath  the  machine.  It  will  then  crumble 
because  of  insufficient  bearing  surface  to  carry  the  imposed  weight. 
The  sulphur  having  been  properly  placed  and  having  set,  the  nuts 
are  then  screwed  down  on  the  bolts,  and  the  machine  is  secure. 

Belting.  The  shafting  and  machines  are  usually  driven  by  belt- 
ing. Leather  is  the  material  generally  used,  and  the  belting  may  be 
from  single  to  six-ply  in  any  suitable  width.  Single  belting  has  a 
flesh  and  a  grain  or  hair  side,  and  should  be  run  with  the  grain  side  in 
contact  with  the  pulley.  The  ends  are  cut  square,  and  fastened  by 
hooks,  coiled  wire,  or  rawhide  lacing. 

Leather  belting  is  injured  by  water,  steam,  oil,  and  temperature 
above  110°  F.  Where  such  conditions  exist,  cotton  belts  faced  with 
thin  leather,  or  rubber  belts,  may  be  used.  These  belts  are  cheaper 
than  leather,  are  about  as  strong,  and  will  transmit  power  as  effec- 
tively; but  they  will  not  stand  mutilation  of  the  edges.  This  is  a 
point  of  prime  importance,  and  prohibits  their  use  in  many  cases. 

The  power  transmitted  by  a  belt  is  directly  proportional  to  its 
speed  and  width.  A  safe  rule  is  to  allow  one  horsepower  for  a  speed 
of  1,000  feet  per  minute,  with  a  single  thick  belt  one  inch  wide.  This 
is  a  more  liberal  allowance  in  favor  of  the  belt  than  is  usually  given, 
but  will  increase  the  life  of  the  belt  in  far  greater  proportion  than  the 
increase  in  first  cost.  Double  belts  will  transmit  about  one  and  one- 
half  times  as  much  power  as  single  belts.  The  above  rule  applies  to 
belts  running  over  pulleys  of  equal  diameter,  or,  in  other  words,  to 
cases  where  the  arc  of  contact  is  180  degrees.  For  smaller  arcs  of 
contact,  use  the  coefficients  found  in  the  following  tabulation : 

Degrees:  90    100    110    120    130    140    150    160    170    180    200 

Coefficient:       .65     .70     .75     .79     .83     .87     .91     .94     .97     1.     1.05 

To  increase  the  power  transmitted,  either  increase  the  speed  of 
the  belt  by  using  larger  pulleys,  or  use  a  wider  belt. 

Example.  A  3-inch  single  belt  is  running  over  a  24-inch  driving 
pulley  which  makes  200  r.p.m.  (revolutions  per  minute).  How 
many  h-p.  will  it  transmit? 


MACHINE  SHOP  WORK  191 

Solution.  The  circumference  of  the  pulley  in  feet  is  2  X  3. 1416  = 
6.2832  feet.  As  the  speed  of  the  pulley  is  200  r.p  m.,  the  speed  of 
the  belt  will  be  200X6.2832  =  1,256.64  feet  per  minute.  For  every 
inch  of  width,  it  will  transmit  1,256.64-^1,000  =  1.25664  h-p. 
Then  a  3-inch  belt  will  transmit  3X1.25664  =  3.76992  h-p. 

Ans.     3.75  h-p.  (approximately) 

Example.  It  is  desired  to  increase  the  h-p.  in  the  above  example 
to  5  h-p.  How  may  it  be  done? 

Solution,  (a)  By  using  a  wider  belt  in  the  proportion  of 
3.75  to  5.  3.75  :  5  :  :  3  :  4.  Ans.  By  using  a  4-inch  belt 

(b)  By  using  a  larger  pulley  in  the  same  proportion.    3.75  : 
5  :  :  24  :  32.  Ans.     By  using  a  32-inch  pulley 

(c)  By  using  a  double  belt.    1  : 1.5  :  :  3.75  :  5.63.    This  would 
give  a  little  better  result  than  required. 


FELLOWS  GEAR  SHAPER  CUTTING  SPUH  4i£.iK 

Courtesy  of  Fellows  Gear  Shaper  Company,  Spring fiua,  Vermont 


/I/)  MACHINE  SHOP  WORK 


PART  IV 


GEAR  CUTTING 

Theory  of  Toothed  Gearing.  The  fundamental  principle  of 
toothed  gearing  is  that  of  two  cylinders  or  portions  of  cones  with  their 
surfaces  in  contact,  and  rolling  together  in  opposite  directions. 

The  first  condition,  that  of  cylinders,  is  shown  in  Fig.  258, 
representing  the  two  cylinders  A  and  B,  the  axes  of  both  being  in  the 
same  plane  and  parallel,  and  the  periphery  of  the  cylinders  in  con- 
tact. It  is  evident  that  if  the  cylinder  A  be  rotated  in  the  direction 
of  the  arrow,  the  frictional  contact  will  cause  the  cylinder  B  to 
rotate  in  the  opposite  direction. 

The  second  condition,  that  of  cones,  is  shown  in  Fig.  259,  rep- 
resenting the  two  cones  A  and  B,  the  axes  of  both  being  in  the  same 
plane,  but  at  right 
angles  to  each  other,  and 
the  outer  surfaces  of  the 
cones  in  contact.  The 
action  is  the  same  as 
that  of  Fig.  258. 

It  will  also  be  evi- 

Fig.  25S.     Two  Cylinders  in  Contact, 

dent  that  if  the  cylin- 
ders in  Fig.  258  are  of  equal  diameters,  and  Consequently  of  equal 
circumferences,  the  rotation  of  A  through  a  complete  revolution  will 
produce  a  complete  revolution  of  B.  If  A  is  one-half  the  diameter 
of  B,  the  latter  will  make-  but  half  a  revolution  to  one  complete 
revolution  of  A;  while,  if  the  cylinder  B  is  one-half  the  diameter  of 
A,  it  will  make  two  complete  revolutions  to  one  of  the  cylinder  A. 
This  proposition  provides  for  no  slipping  of  the  cylinders  on 
each  other.  For  the  purpose  of  transmitting  power,  the  faces  of 
these  cylinders  are  provided  with  teeth,  which  are  cut  parallel  to 
the  axes  of  the  cylinder;  the  teeth  of  each  cylinder  interlock  with 
those  of  the  other  and  effectually  prevent  any  slipping.  By  this 


194 


MACHINE  SHOP  WORK 


means  we  produce  a  pair  of  spur  gears.  In  the  case  of  the  two 
cones,  or  a  suitable  portion  of  them,  if  the  teeth  are  formed 
radiating  from  the  apex  of  the  cone,  they  become  a  pair  of  bevel  gears. 


Fig.  259.     Two  Cones  in  Contact 


The  simplest  form  and  the  one  in  most  common  use,  is  the  spur 
gear.  All  other  forms  are  but  modifications  of  it  in  one  way  or 
another,  the  general  principle  and  the  principle  upon  which  the  teeth 
are  formed  being  practically  the  same  in  every  form  of  gear  in  use. 


Fig.  260.     Tooth  Gears  in  Contact 

It  therefore  becomes  necessary  to  study  carefully  the  essential 
features  of  the  spur  gear,  and  to  understand  thoroughly  its  con- 
struction. 

It  being  one  of  the  conditions  of  the  problem  that  the  surfaces 
of  the  cylinders  shall  remain  in  contact,  as  shown  in  Fig.  258,  teeth 


MACHINE  SHOP  WORK 


195 


must  not  be  formed  in  their  surfaces  by  cutting  grooves  in  them,  for 
the  reason  that,  to  cause  the  teeth  to  interlock,  it  would  be  necessary 
to  move  their  axes  closer  together,  thus  overlapping  the  original 
surfaces.  Teeth  cannot  be  added  to  the  cylinders  as  this  would 
necessitate  moving  the  cylinders  farther  apart,  thus  separating  the 
contact  surfaces. 

This  being  the  case,  the  teeth  must  be  formed  by  a  combination 
of  both  the  above  methods,  cutting  the  grooves  one-half  the  depth  of 
the  proposed  teeth,  and  adding  between  the  spaces  thus  formed  an 
equal  amount  to  complete  the  partially  formed  teeth.  They  will  then 


Fig.  2G1.     Names  of  Tooth  Parts 

present  the  forms  shown  in  Fig.  260,  the  added  portions  being  dis- 
tinguished by  being  drawn  solid  instead  of  being  sectioned.  They 
are  called  the  addendum. 

The  teeth  now  interlock  properly  by  falling  into  the  spaces,  the 
original  surfaces  of  the  cylinders  remaining  on  the  contact  line;  and 
the  diameters  of  these  cylinders  still  give  the  base  circles  for  all 
calculations  as  to  speed,  numbers,  and  dimensions  of  teeth  and 
similar  purposes.  These  circles  are  called  the  pitch  circles.  When 
a  pair  of  gears  vary  in  diameter  by  a  ratio  of  1  to  3,  or  more,  the 
larger  is  called  the  wheel,  and  the  smaller  the  pinion. 

Names  of  the  Tooth  Parts.  The  names  of  the  tooth  parts  are 
given  in  the  diagram,  Fig.  261,  in  order  that  the  student  may  become 
perfectly  familiar  with  the  technical  terms  used  in  describing  or 


196  MACHINE  SHOP  WORK 

referring  to  the  teeth  of  gears,  and  the  methods  of  calculating, 
designing,  and  drawing  their  various  parts. 

The  pitch  diameter  is  the  diameter  of  the  pitch  circle. 

The  addendum  circle  has  the  same  diameter  as  the  outside  diam- 
eter— that  is,  the  diameter  over  the  points  of  the  teeth. 

The  dedendum  circle,  or  root  circle,  is  the  circle  at  the  bottom  of 
the  teeth. 

The  pitch  is  the  distance  from  center  to  center  of  the  teeth  when 
measured  on  the  pitch  circle.  When  thus  measured,  it  is  called  the 
circular  pitch. 

The  face  of  the  tooth  is  that  portion  of  the  curve  outside  of  the 
pitch  circle. 

The  flank  of  the  tooth  is  that  portion  of  the  curve  within  the 
pitch  circle. 

The  thickness  of  the  tooth  is  its  width,  taken  as  the  chord  of  an 
arc  of  the  pitch  circle. 

The  space  is  the  distance  between  adjacent  teeth,  measured  as 
the  chord  of  an  arc  of  the  pitch  circle. 

DESIGNING  GEARS 

Fixed  Pitch  Method.  Formerly  the  teeth  of  gears  were  designed 
on  the  basis  of  a  fixed  distance  representing  the  pitch.  This  was 
usually  based  on  the  common  fractions  of  an  inch  or  multiples  of 
them,  as  J,  f ,  J,  f ,  f ,  J,,l,  li,  1 J,  If,  2, 2J,  3  inches,  etc.  The  desired 
number  of  teeth  multiplied  by  the  given  pitch  gave  the  circum- 
ference; and  the  distance  thus  found  divided  by  3.1416  gave  the 
diameter  of  the  pitch  circle. 

The  pitch  was  divided  into  15  parts,  7  of  which  represented  the 
thickness  of  the  teeth  and  8  the  width  of  the  space.  To  find  the 
length  of  the  teeth,  the  pitch  was  divided  into  10  parts,  of  which 
seven  represented  the  length  of  the  teeth — 3  parts  being  that  portion 
outside  of  the  pitch  circle  and  4  parts  the  length  inside  of  it,  1  part 
being  allowed  for  bottom  clearance.  Such  a  method  involved  many 
tedious  calculations,  and  in  due  time  mechanical  engineers  devised 
a  method  simpler  and  more  convenient,  which  has  of  late  years 
been  exclusively  used  for  this  purpose. 

Diametral  Pitch  Method,  By  this  system  the  pitch  is  desig- 
nated by  a  number  instead  of  giving  the  length  of  the  pitch  in  inches*, 


MACHINE  SHOP  WORK  197 

This  number  indicates  the  number  of  teeth  for  each  inch  of  diameter  of 
the  pitch  circle.  Therefore,  if  the  diametral  pitch  is  6,  and  the 
diameter  of  the  pitch  circle  is  10  inches,  the  gear  will  have  6X10, 
or  60  teeth.  Tims  we  know  that  if  the  pitch  is  6,  or,  as  usually 
expressed,  "6  pitch'',  and  the  gear  has  60  teeth,  the  pitch  diameter  is 
60^-  6,  or  10  inches.  And  if  the  gear  has  60  teeth,  and  the  diametef 
of  the  pitch  circle  is  10  inches,  the  pitch  is  60-J-10,  or  6  pitch.  We 
have  then  the  three  following  simple  rules: 

(1)  Multiply  the  diameter  of  the  pitch  circle  by  the  diametral  pitch 
to  get  the  number  of  teeth. 

(2)  Divide  the  number  of  teeth  by  the  diameter  of  the  pitch  circle  to 
get  the  diametral  pitch. 

(3)  Divide  the  number  of  teeth  by  the  diametral  pitch  to  get  the 
diameter  of  the  pitch  circle. 

The  proportions  of  tooth  parts  are  determined  by  methods  quite 
as  simple  as  the  question  of  pitch.  They  are  as  follows: 

The  addendum  is  equal  to  one  inch  divided  by  the  diametral 
pitch ;  hence  that  on  a  6-pitch  gear  will  be  J  of  an  inch. 

The  dedendum  is  a  like  distance  increased  by  the  clearance, 
which  is  equal  to  one-tenth  of  the  thickness  of  the  tooth  on  the 
pitch  circle. 

The  thickness  of  the  tooth,  and  the  width  of  the  space  at  the 
pitch  line,  are  not  determined  by  a  rule  similar  «fo  that  given  in  the 
former  method.  In  accurately  cut  gears,  the  width  of  the  space 
exceeds  the  thickness  of  the  tooth  by  only  as  much  as  may  be  neces- 
sary to  permit  the  gear  teeth  to  roll  freely  together,  and  need  not  be 
over  .03  of  the  circular  pitch.  In  cut  gears  for  ordinary  purposes, 
this  amount  may  be  doubled;  while  in  gears  having  cast  teeth,  it  may 
need  to  be  as  great  as  0.10  of  the  circular  pitch  depending,  of  course, 
upon  the  accuracy  of  the  casting. 

In  order  to  afford  a  correct  impression  of  the  relative  dimensions 
of  spur-gear  teeth  of  different  diametral  pitches,  Fig.  262  is  givenj 
in  which  the  gear  teeth  are  shown  full  size.  These  are  the  more 
common  pitches.  Those  larger  than  here  shown  are  usually  1,  1J, 
2,  2J,  and  3  pitch. 

Development  of  Gear=Tooth  Curves.  Epicycloidal  Curve. 
This  is  a  matter  of  considerable  importance,  and  should  be  thor- 
oughly understood  in  connection  with  the  work  of  gear  cutting:. 


198 


MACHINE  SHOP  WORK 


Fig.  262.     Proportions  of  Teeth  of  Different  Diametral  Pitches 


MACHINE  SHOP  WORK  199 

Formerly  the  epicycloidal  curve  was  considered  to  be  the  most 
appropriate,  since  it  is  traced  by  a  fixed  point  in  the  periphery  of 
one  cylinder  rolling  upon  another.  This  is  a  perfectly  correct 
theory,  and  many  excellent  gears  are  still  made  with  this  form  of 
teeth. 

There  is  one  serious  disadvantage,  however,  in  gears  w^ith  teeth 
so  formed.  In  gears  of  much  variation  in  diameter  the  teeth  are  so 
different  from  each  other  in  form  that  they  will  not  run  properly  with 
other  gears  varying  much  in  diameter  from  the  particular  gear 
designed  to  run  with  them.  The  result  was  a  great  variety  of  curves 
in  gears  with  cast  teeth,  and  of  cutters,  wrhen  the  teeth  were  cut  from 
solid  blanks,  which  often  proved  very  troublesome  and  expensive; 
and  many  efforts  were  made  to  produce  some  more  satisfactory 
method. 

Involute  Curve.    The  involute  curve  was  experimented  with, 
and  satisfactory  results  were  obtained.     It  possesses  several  advan- 
tages over  the  epicycloidal  curve,  which  may  be  stated  as  follows: 
A  single  curve  is  sufficient,  while  in  the  epicycloid  a  com- 
pound curve  was  necessary. 

Undercutting  the  flanks  of  the  teeth  is  not  necessary. 
Gears  of  any  number  of  teeth  will  run  properly  with  other 
gears  of  any  number  of  teeth  indiscriminately.    This 
is  a  very  great  advantage  in  many  respects. 
Cutters  properly  formed  to  cut  involute  teeth  may  be  used  for 
gears  of  a  considerable  variation  as  to  numbers  of  teeth.    This  fact 
greatly  reduces  the  number  of  cutters  of  each  pitch  that  are  required 
or  cutting  a  complete  range  of  work  from  pinions  of  12  teeth  to  a 
rack.    Where  8  cutters  are  required,  the  ranges  of  work  are  as  follows : 
No.  1  will  cut  from  135  teeth  to  a  rack 
No.  2  will  cut  from    55  teeth  to  134  teeth 
No.  3  will  cut  from    35  teeth  to    54  teeth 
No.  4  will  cut  from    26  teeth  to    34  teeth 
No.  5  will  cut  from    21  teeth  to    25  teeth     . 
No.  6  will  cut  from    17  teeth  to    20  teeth 
No.  7  will  cut  from    14  teeth  to    16  teeth 
No.  8  will  cut  from    12  teeth  to    15  teeth 

The  involute  curve  is  generated  mechanically  by  a  point  at  the 
nd  of  a  cord  which  is  unwound  from  the  surface  of  a  circular  disc 


200 


MACHINE  SHOP  WORK 


or  a  cylinder.  The  curve  is  generated  as  shown  in  Fig.  263.  A  is 
an  arc  representing  the  cylinder,  with  its  center  at  B.  From  the 
vertical  line  EC,  and  on  the  arc  A,  are  spaced  at  equal  distances  the 
points  ./,#,3,  4,  5,  6,  7, 8.  Radial  lines  are  drawn  from  each  of  those 
to  the  center  B.  From  each  of  these  points  are  drawn  the  lines  a,  b, 
c,  d,  e,  f,  g,  which  are  tangent  to  the  arc  A .  From  2  as  a  center,  and 
with  the  distance  1-2,  the  portion  of  the  required  curve  from  the  arc 

to  the  line  a  is  traced. 
From  3  as  a  center,  with 
the  distance  1-3,  the  por- 
tion 'of  the  curve  from  a 
to  b  is  traced.  And  so 
on,  until  the  involute 
curve  D  is  traced  as  far 
as  may  be  necessary. 

In  the  practical  use 
of  the  involute  curve  thus 
determined,  an  arc  of 
such  radius,  and  with  its 
center  so  located  as  to 
approach  closely  the  true 
curve,  is  generally  used, 

Fig.  263.     Generation  of  Involute  an(J    f  ormg    not  only   the 

face  but  the  flank  of  the  tooth.  For  this  purpose,  gears  are  classi- 
fied according  to  the  number  of  teeth  as  follows: 

First  Class —   all  gears  having  over  30  teeth 

Second  Class — all  gears  having  19  to  29  teeth,  inclusive 

Third  Class —  all  gears  having  12  to  18  teeth,  inclusive 

Laying  Out  Teeth.  The  method  of  laying  out  teeth  of  the  first 
class  is  shown  in  Fig.  264.  The  pitch  circle  A  has  its  center  at  B, 
upon  the  vertical  line  BC.  From  this  center  the  addendum  circle  D 
and  the  dedendum  or  root  circle  E  are  drawn.  From  the  vertical 
line  BC,  and  to  the  right  and  left  on  the  pitch  circle  A,  are  laid  off 
the  centers  of  the  teeth,  and  the  radial  lines  1,  2,  3,  4>  &  drawn. 
Through  a,  the  point  of  intersection  of  the  vertical  line  BC  and  the 
pitch  circle  A,  is  drawn  the  arc  F,  of  one-half  the  radius  of  the  pitch 
circle.  Through  the  point  of  intersection  b  of  this  arc  with  the 


MACHINE  SHOP  WORK 


201 


radial  line  4 — equal  to  the  pitch  from  the  vertical  line  BC — the  base 
circle  G  is  drawn.  To  the  left  of  the  vertical  line  BC  and  on  the 
pitch  circle  A,  is  set  off  one-half  the  thickness  of  the  tooth — one- 
fourth  the  pitch — to  the  point  c.  With  a  radius  equal  to  be,  and 
from  b  as  a  center,  the  arc  d  is  drawn,  representing  the  face  and  flank 
of  one  side  of  the  center  tooth.  With  the  same  radius,  and  with 
the  intersections  of  the  radial  lines  19  2,  8,  4>  and  5  with  the  base 

IT-    •'  / 


Fig.  2(34.     Laying  Out  Large  Gears 

circle  G,  the  arcs  representing  the  faces  and  flanks  of  the  other  teeth 
are  drawn.  The  bottom  clearance  is  equal  to  one-tenth  the  thick- 
ness of  the  tooth  on  the  pitch  circle;  therefore  the  arcs  d  are  brought 
down  to  within  this  distance  of  the  dedendum  or  root  circle  E  and 
completed  with  a  small  arc  of  a  radius  equal  to  the  clearance.  This 
method  is  adapted  to  the  teeth  of  gears  of  the  first  class  (30  teeth  or 
over),  and  will  be  found  applicable  to  gears  cut  from  solid  blanks  or 
those  with  cast  teeth,  making  proper  allowances  for  clearance  in 
the  latter  case. 

Gears  of  less  than  30  teeth  comprise  the  other  two  classes.     It 
is  readily  seen  that  as  the  gears  are  very  much  reduced  in  diameter, 


202 


MACHINE  SHOP  WORK 


the  angle  at  which  the  teeth  of  one  enter  the  spaces  of  the  other  will 
require  a  modification  in  the  form  of  the  teeth. 

The  method  of  forming  the  teeth  of  gears  of  the  second  class  is 
shown  in  Fig.  265,  and  follows  the  method  shown  in  Fig.  264,  up  to 


Fig.  265.     Laying  Out  Gears  of  Second  Class 

the  location  of  the  center  for  the  arc  forming  the  face  of  the  tooth. 
In  this  case  it  is  located  at  the  intersection  of  the  tooth  curve  d  with 
the  base  circle  G;  and  the  flanks  of  the  tooth  are  radial  instead  of 

parallel  lines. 

The  method  of  form- 
ing the  teeth  of  gears  of 
the  third  class  is  shown 
in  Fig.  266.  This  method 
proceeds  in  the  same 
manner  as  shown  in  Figs. 
264  and  265  as  described 
above,  up  to  the  loca- 
tion of  the  center  for  the 
arc  forming  the  face  of 

Fig.  266.     Laying  Out  Small  Gears 

the  tooth.     In  the  first 

case,  this  was  at  the  intersection  of  the  arc  F  with  a  radial  line  drawn 
through  the  center  of  the  adjacent  tooth,  and  for  second-class  gears 
it  was  at  the  intersection  of  the  arc  F  with  the  flank  of  the  tooth. 
In  this  case  it  is  located  at  the  intersection  of  the  arc  F  with  a  radial 


MACHINE  SHOP  WORK 


203 


line  drawn  through  the  center  of  the  space.  The  curve  d  is  there- 
fore of  relatively  shorter  radius.  Instead  of  prolonging  the  curve  d 
to  the  clearance  arc,  the  flank  of  the  tooth  is  formed  by  straight 
lines  //  parallel  to  the  vertical  line  B  C  and  tangent  'to  the  curve  d. 
These  three  methods  of  describing  the  forms  of  involute  teeth, 
for  the  three  classes  described,  produce  curves  very  closely  corre- 


Fig.  267.     Laying  Out  Teeth  of  Internal  Gear 

sponding  to  the  theoretically  correct  involute  curves,  and  quite 
sufficient  for  all  practical  purposes  for  which  gears  having  teeth  cut 
with  circular  cutters  are  intended. 

Internal  Gears.  Internal  gears  must  frequently  be  used  when 
there  is  not  room  for  spur  gears  or  when  the  nature  of  the  work  or 
the  design  of  the  machine  of  which  they  are  a  part  renders  this  form 
necessary  or  advisable.  Thus  far  we  have  considered  gears  repre- 
sented by  cylinders  whose  outer  surfaces  rolled  together.  In  the  case 


204 


MACHINE  SHOP  WORK 


of  the  internal  gear  the  outer  surface  of  a  smaller  cylinder  is  supposed 
to  roll  on  the  internal  surface  of  a  larger  cylinder.  Therefore, 
the  larger  gear  will  have  teeth  projecting  inwardly  or  toward  its  axis. 
Theoretically  the  proper  curve  for  the  teeth  of  an  internal  gear 
will  be  the  internal  epicycloid,  as  this  is  the  curve  traced  by  a  point 


Fig.  268.     First  Method  of  Laying  Out  Teeth  of  Rack 

on  the  surface  of  one  cylinder  rolling  inside  of  another  cylinder. 
The  method  of  laying  out  the  teeth  is  shown  in  Fig.  267.  The  pitch 
circle  A,  addendum  circle  Z),  and  dedendum  circle  E  are  drawn  as 
in  the  previous  examples,  the  vertical  line  EC  indicating  the  center 
of  the  work.  The  pitch  is  spaced  off  on  the  pitch  circle  A,  each  way 
from  the  line  BC,  and  the  thickness  of  the  teeth  and  width  of  the 


Fig.  269.     Accurate  Method  of  Laying  Out  Teeth  of  Rack 

spaces  indicated.  At  the  point  of  intersection  of  the  vertical  line 
BC  with  the  pitch  circle  A,  is  drawn  an  inclined  line  FF  at  an  angle 
of  78  degrees  to  the  vertical  line  BC.  Through  the  point  of  inter- 
section a  of  this  line  with  the  center  line  4  of  the  adjacent  tooth,  the 
base  circle  H  is  drawn,  giving  the  location  of  the  centers  for  the 
faces  of  the  teeth,  which  are  described  by  the  arc  of  the  radius  ah. 


MACHINE  SHOP  WORK  205 

In  a  similar  manner  the  line  GG  is  drawn  at  an  angle  of  87  degrees 
with  the  vertical  line  BC;  and  through  the  point  of  intersection  c 
with  the  radial  line  4,  the  base  circle  J  is  drawn,  which  gives  the  loca- 
tion of  the  centers  for  the  flanks  of  the  teeth,  which  are  described  by 
the  arc  of  the  radius  cd.  The  arc  joining  the  flank  curve  with  the 
dedendum  circle  is  the  same  as  in  previous  examples. 

Teeth  of  Racks.  Two  methods  are  in  use  for  drawing  the  form 
of  teeth  for  racks.  The  first  method  is  shown  in  Fig.  268.  The  pitch 
line  Ay  addendum  line  B,  and  dedendum  line  C  are  straight  lines 
located  as  before  described.  The  teeth  and  spaces  are  set  off  at 
equal  distances  on  the  pitch  line  A .  The  sides  of  the  teeth,  including 
face  and  flank,  are  composed  of  straight  lines  aa  inclined  at  an  angle 
of  14 \  degrees  from  a  vertical  line  or  75  J  degrees  from  the  pitch  line  A . 
The  lower  ends  of  these  lines  are  joined  to  the  dedendum  line  by 
small  arcs,  as  previously  described.  While  this  form  of  tooth  is  not 
theoretically  correct,  many  racks  running  with  gears  having  involute 
teeth  are  so  constructed,  and  they  operate  satisfactorily  for  many 
kinds  of  work.  However,  the  second  method,  Fig.  269,  is  preferable 
for  accurate  work  and  for  carrying  heavy  loads.  The  principal 
lines  A ,  J9,  and  C,  and  the  spacing  of  the  teeth  are  the  same  as  in 
Fig.  268.  The  vertical  line  DD  is  erected  at  the  side  of  one  of  the 
teeth.  Through  the  point  a  of  the  intersection  of  this  line  with  the 
pitch  line  A  is  drawn  the  inclined  line  EE  at  an  angle  of  78  degrees 
with  the  vertical  line  DD.  Through  the  point  b  of  the  intersection 
of  this  line  with  the  vertical  line  3  of  the  side  of  the  adjacent  tooth 
is  drawn  the  base  line  F,  which  locates  the  centers  for  the  arc  with 
the  radius  be,  forming  the  face  of  the  tooth.  Through  the  point  d 
of  the  intersection  of  the  line  EE  with  the  vertical  line  #,  at  the  left 
of  the  tooth,  the  base  line  G  is  drawn,  locating  the  centers  for  the 
arc  with  the  radius  de,  forming  the  flank  of  the  tooth.  The  lower 
ends  of  these  arcs  are  joined  to  the  dedendum  line  C  by  small  arcs, 
as  previously  described. 

Table  X  gives  the  various  dimensions  of  the  parts  of  gear  teeth 
calculated  for  involute  teeth  designed  upon  the  diametral-pitch 
system.  It  is  useful  in  comparing  the  different  dimensions  of  the 
same  pitch  with  one  another,  and  in  comparing  similar  dimensions 
used  in  the  same  pitch;  and  it  will  enable  the  student  to  avoid 
making  tedious  calculations  in  each  instance. 


206 


MACHINE  SHOP  WORK 


TABLE  X 
Involute  Gear  Tooth  Parts 


DIAMETRAL 
PITCH 

CIRCULAR 
PITCH 

THICKNESS 
OF  TOOTH 

ADDENDUM 

WORKING 
DEPTH 

WHOLE 
DEPTH 

1 

3.1416 

1.5708 

1.0000 

2.0000 

2.1571 

1* 

2.0944 

1.0472 

.6666 

1  .  3333 

1.4381 

2 

1.5708 

.7854 

.5000 

1.0000 

1.0785 

2i 

1.2566 

.6283 

.4000 

.8000 

.8628 

3 

1.0472 

.5236 

.3333 

.6666 

.7190 

4 

.7854 

.3927 

.2500 

.5000 

.5393 

5 

.6283 

.3142 

.2000 

.4000 

.4314 

6 

.5236 

.2618 

.1666 

.3333 

.3463 

7 

.4488 

.2244 

.1429 

.2857 

.3080 

8 

.3927 

.1963 

.1250 

.2500 

.2696 

9 

.3491 

.1745 

.1111 

.2222 

.2396 

10 

.3142 

.1571 

.1000 

.2000 

.2157 

12 

.2618 

.1309 

.0833 

.1666 

.1796 

14 

.2244 

.1122 

.0714 

.1429 

.1540 

16 

.1963 

.0981 

.0625 

.1250 

.1348 

18 

.1745 

.0871 

.0555 

.1111 

.1198 

20 

.1571 

.0785 

.0500 

.1000 

.1078 

24 

.1309 

.0654 

.0416 

.0833 

.0898 

Attention  is  directed  to  the  following  characteristics  of  these 
dimensions: 

(a)  The  thickness  of  the  tooth  equals  one-half  the  circular  pitch. 

(b)  The  addendum  equals  1  (one  inch),  divided  by  the  diametral  pitch. 

(c)  The  working  depth  of  the  tooth  is  twice  the  addendum,  as  the  adden- 
dum and  dedendum  are  equal. 

(d)  The  whole  depth  of  the  tooth  is  the  working  depth  plus  one-tenth 
of  the  thickness  of  the  tooth,  which  is  the  clearance.     The  radius  of  the  clear- 
ance arc  is  one-seventh  of  the  distance  between  the  points  of  adjacent  teeth. 


Fig.  270.     Bevel  Gears  at  Various  Angles 

Bevel  Gears.    In  the  treatment  of  spur  gears,  we  have  consid- 
ered them  fundamentally  as  cylinders  rolling  upon  each  other  (ordi- 


MACHINE  SHOP  WORK 


207 


nary  spur  gears)  or  a  cylinder  rolling  on  the  inner  surface  of  a  larger 
one  (internal  gears).  We  now  come  to  consider  cones  of  various 
diameters  and  relative  proportions  rolling  together,  as  shown  in 
Fig.  259.  The  surfaces  of  the  cones  represent  their  pitch  circles  in 
the  same  manner  as  the  cylinders.  While  spur  gears  must  have  their 
shafts  always  parallel,  bevel  gears  may  be  designed  to  run  properly 
at  any  angle  from  parallel  to  150  degrees.  In  Fig.  270  are  shown 
several  pairs  of  typical  bevel  gears  with  their  shafts  at  different  angles. 
Those  of  90  degrees  are  the  more  common.  The  pair  shown  at  4 


Fig.  271.     Cross-Section  of  Pair  of  Bevel  Gears 

are  unusual  but  sometimes  necessary,  and  operate  quite  as  well  as 
the  others.  In  this  case  the  larger  gear  is  an  internal  bevel  gear. 

When  two  bevel  gears  of  the  same  diameter  and  number  of  teeth 
run  together,  they  are  called  miter  gears,  although  this  term  is  more 
likely  to  be  applied  to  those  whose  shafts  are  at  an  angle  of  90  degrees 
to  each  other. 

Fig.  271  is  a  cross-section  of  a  pair  of  bevel  gears,  and  is  designed 
to  illustrate  the  principles  applicable  to  the  cutting  of  gears.  The 
lines  A  A  and  BB  are  the  center  lines  of  the  two  shafts,  their  point 
of  intersection  being  the  apex  of  each  of  the  cones  representing  the 
pitch  surfaces.  The  line  CC  is  parallel  to  A  A  and  at  a  distance  from 
it  equal  to  half  the  pitch  diameter  of  the  larger  gear.  The  line  DD 


208  MACHINE  SHOP  WORK 

is  parallel  to  the  line  BB,  and  distant  from  it  one-half  the  pitch  diam- 
eter of  the  smaller  gear.  Between  the  points  of  intersection  of  the 
lines  AA  and  BB,  and  of  CO  and  DD,  the  pitch  line  EE  is  drawn, 
giving  the  line  of  contact  between  the  two  cones.  The  outline  of  the 
cones  is  completed  by  the  line  FF.  The  outer  and  inner  ends  of 
the  teeth  are  lines  at  right  angles  to  the  pitch  lines;  and  upon  the 
outer  tooth  lines  the  depths  of  the  teeth  above  and  below  the  pitch 
lines  are  set  off;  and  the  lines  a  and  6,  for  the  top  and  bottom  of  the 
teeth,  are  drawn  radially  from  the  common  apex  of  the  cones  at  c. 
The  various  dimensions  of  the  teeth  are  laid  off  at  the  large  or  outer 
ends  of  the  teeth,  and  are  taken  from  Table  X. 

To  facilitate  the  proper  cutting  of  bevel  gears,  the  drawing  should 
give  the  face  angle  a  and  the  cutting  angle  b  for  each  gear,  and 
the  depth  of  the  teeth  at  the  outer  end.  The  angles  should  be  so 
expressed  that  a  bevel  protractor  may  be  set  against  the  hub  of  the 
gear,  and  its  arm  upon  the  face  angle  and  cutting  angle,  to  verify 
their  correctness.  When  the  shafts  are  at  right  angles,  the  sum  of 
the  edge  angles  will  equal  90  degrees,  and  the  sum  of  the  face  angles 
and  edge  angles  will  be  equal. 

The  angles  may  be  determined  by  this  method,  for  the  angle  of 
the  pitch  line  FF  with  the  face  of  the  hub  (or  the  line  DD  parallel 
to  it),  we  may  consider  as  a  right-angled  triangle  FFD.  Divide 
the  height  by  the  base,  and  the  quotient  will  be  the  natural  tangent. 
From  the  table  of  tangents  we  get  the  angle  in  degrees  and  minutes. 

Thus,  suppose  the  base  is  5  inches,  and  the  height  2.5  inches, 
then  2.5  -T-  5  =  0.5,  which  is  the  tangent.  In  the  table  of  tangents  we 
find  the  nearest  number  is  .50004,  whose  corresponding  angle  is  26 
degrees  34  minutes.  The  value  of  any  angle  expressed  in  degrees  and 
minutes  may  be  determined  in  the  same  manner  if  the  base  and 
height  are  known. 

Worm  Gearing.  This  is  a  term  used  to  describe  the  device 
consisting  of  a  gear  similar  to  a  spur  gear  driven  by  a  worm — that  is,  a 
cylinder  upon  whose  surface  is  a  thread  fitting  into  the  teeth  of  the 
gear.  The  relative  speed  of  the  worm  and  gear  are  found  by  dividing 
the  number  of  teeth  in  the  gear  by  the  number  of  threads  on  the 
worm.  Worms  are  always  understood  to  be  of  single  thread,  unless 
otherwise  specified.  The  pitch  of  a  single-threaded  worm  is  equal 
to  the  circular  pitch  of  the  worm  gear,  and  vice  versa.  The  shafts 


MACHINE  SHOP  WORK 


209 


of  a  worm  and  worm  gear  are  usually  (but  not  necessarily)  lit  right 
angles  to  each  other. 

A  simple  form  of  worm  gear  is  shown  in  Fig.  272,  in  which  the 
worm  B  has  a  single  thread  having  an  inclination  on  each  side  of  14^ 
degrees,  or  what  is  usually  called  a  "29-degree"  thread.  The  teeth 
of  the  worm  are  cut  to  a  similar  form,  and  the  pitch  circle  located  the 


Fig.  272.     Simple  Worm  Gear 

same  as  in  a  spur  gear;  but,  as  the  lines  of  the  thread  of  the  worm  are 
not  at  right  angles  to  the  axis,  but  at  an  angle  due  to  the  pitch  of  the 
thread,  the  teeth  of  the  worm  gear  must  be  cut  at  such  an  angle  as  to 
be  tangent  to  the  curved  line  of  the  thread,  as  shown  at  a.  The 
calculations  for  this  worm  gear  are  made  the  same  as  for  a  spur  gear. 
Thus  the  pitch  of  the  thread,  multiplied  by  the  number  of  teeth,  will 
give  the  circumference  of  the  pitch  circle,  which  amount,  divided  by 
3.1416,  will  give  its  diameter.  In  consequence  of  the  relatively  large 


210 


MACHINE  SHOP  WORK 


diameter  of  the  worm  compared  with  the  thickness  of  the  worm  gear, 
enclosing  an  angle  of  only  14  degrees  on  the  pitch  line,  the  teeth  of 
the  latter  may  be  cut  on  a  line  parallel  to  its  axis,  as  they  will  con- 
form quite  nearly  to  the  curvature  of  the  thread  of  the  worm.  This 
is  the  simplest  form  of  a  worm  gear,  and  one  not  often  used,  on 
account  of  the  small  amount  of  power  it  is  able  to  transmit. 

The  usual  practice,  particularly  where  considerable  power  is 
to  be  transmitted,  is  to  design  the  worm  wheel  as  shown  in  Fig.  27o, 

by  which  a  much  greater  area  of 
contact  is  secured,  but  making  a 
much  more  complicated  form, 
and  one  in  which  some  new  con- 
ditions must  be  considered.  In 
this  case  the  enclosing  angle  is 
80  degrees,  instead  of  29  degrees, 
as  in  the  former  example.  In 
the  former  example,  the  teeth 
were  cut  as  in  a  spur  gear,  hence 
the  pitch  surface  bb,  Fig.  272, 
was  straight,  and  the  diameter 
of  the  pitch  circle  was  therefore 
measured  as  in  a  spur  gear.  In 
this  case  the  pitch  line  is  con- 
siderably curved,  being  an  80- 
degree  arc  on  the  pitch  circle  a 
of  the  worm.  It  has  sometimes 
been  the  practice  to  calculate  the  pitch  diameter  from  the  point  6, 
usually  called  the  throat  of  the  gear.  It  is  obvious  that  this  is  an 
arbitrary  point,  that  the  number  of  degrees  contained  in  the  enclos- 
ing angle  is  not  considered,  and  that,  for  instance,  if  the  number  of 
degrees  were  much  reduced,  so  as  to  materially  flatten  the  arc,  this 
point  would  vary  considerably  from  its  proper  place.  It  has  been 
found  in  practice  that  if  we  divide  that  portion  of  the  pitch  line  a 
that  lies  between  the  vertical  center  line  xy  and  the  enclosing  angle 
into  three  equal  parts  as  shown,  whatever  may  be  the  enclosing 
angle,  the  point  c  will  indicate  the  correct  diameter  of  the  pitch 
circle.  We  shall  then  have  the  pitch  diameter  at  C,  the  diameter 
at  the  bottom  of  the  teeth  at  D,  and  the  outside  diameter  at  E. 


Fig.  273.     Worm  Gear  with  Large  Enclosing 
Angle 


MACHINE  SHOP  WORK  211 

These  relative  diameters  bear  no  fixed  relation  to  similar  dimen- 
sions of  a  spur  gear,  or  to  those  of  other  worm  gears  of  differing 
proportions. 

To  find  the  angle  of  the  thread,  we  use  the  right-angled  triangle, 
as  shown  in  Fig.  274,  in  which  the  base  equals  the  circumference  of 
the  worm,  the  height  equals  the  pitch  of  the  thread,  and  the  hypothe- 
nuse  is  the  development  of  the  thread  itself.  Mathematically  we 
find  the  angle  of  the  thread  by  dividing  the  pitch  (height)  by  the 
circumference  (base)  to  get  the  tangent  of  the  arc,  and  obtain  the 
angle  from  a  table  of  natural  tangents.  Should  the  worm  have  a 
double  thread,  the  height  of  the  triangle  will  be  twice  as  great. 

Spiral  Gears.  As  has  heretofore  been  stated,  the  spur  gear  has 
its  teeth  cut  in  a  line  parallel  to  the  axis.  If  the  teeth  are  cut  at  an 


C  i  rcum  ference 
Fig.  274.     Diagram  for  Finding  Angle  of  Worm  Thread 

angle  to  the  axis,  and  the  cut  continued  by  the  gradual  rotation  of  the 
gear  blank  as  it  advances,  a  spiral  gear  will  be  produced.  If  the  cut 
is  prolonged,  it  will  finally  make  a  complete  revolution  and  arrive 
at  the  original  line  parallel  to  the  axis  of  rotation.  fne  lead  of  the 
spiral  is  the  distance  from  the  beginning  of  the  cut  to  a  point  where 
the  revolution  is  completed.  The  angle  of  the  spiral  is  found  in  a 
manner  similar  to  that  described  for  the  diagram,  Fig.  274.  As 
applied  to  this  case,  the  rule  will  be :  divide  the  number  of  inches  of  the 
circumference  of  the  cylinder  on  which  the  spiral  is  to  be  cut  by  the 
number  of  inches  in  the  lead,  and  the  quotient  will  be  the  tangent 
of  the  angle  of  the  spiral,  the  angle  being  found  from  a  table  of 
natural  tangents.  Thus  we  have  the  following  rule:  Divide  the 
circumference  by  the  tangent  of  the  angle  to  produce  the  lead;  or  multiply 
the  tangent  by  the  lead  to  produce  the  circumference. 

In  making  calculations  for  spiral  gears,  the  pitch  diameter, 
and  not  the  outside  diameter,  is  understood.  Spiral  gears  have 
several  properties  that ,  should  be  remembered  in  making  calcula- 


212 


MACHINE  SHOP  WORK 


tions  for  them .     It  is  assumed  in  each  case  that  the  gears  are  engaged , 
or  in  mesh,  with  one  another. 

(1)  Two  spiral  gears  of  equal  diameter,  number  of  teeth,  and  angle  of 
teeth,  will  have  the  same  lead  of  spiral. 

(2)  If  two  spiral  gears  are  of  equal  diameter,  one  having  twice  as  many 
teeth  as  the  other,  one  will  have  twice  the  length  of  lead  of  the  other. 

(3)  If  two  spiral  gears  are  of  equal  diameter,  one  having  twice  as  many 
teeth  as  the  other,  the  teeth  of  one  will  have  twice  the  angle  of  the  other. 

(4)  'Two  spiral  gears  of  equal  diam- 
eter, on  parallel  shafts,  will  have  the  same 
angle  of  teeth  on  both. 

(5)  Two  right-hand  spiral  gears  must 
have  the  angles  of  their  shafts  at  an  angle 
equal  to  the  sum  of  the  angles  of  the  teeth 
of  both  gears. 

(6)  One  right-hand  and  one  left-hand 
spiral  gear  must  have  the  angles  of  their  shafts 
equal  to  the  angle  of  the  teeth  of  one  gear, 
less  the  angle  of  the  teeth  of  the  other. 

(7)  If  two  spiral  gears  are  of  equal 
diameter,  one  with  twice  as  many  teeth  as  the 
other,   the  gear  with  the  lesser  number  of 
teeth  will  have  them  at  twice  the  angle  of 
the  other. 

(8)  If  one  of  two  spiral  gears  has  teeth 
at  an  angle  of  45  degrees  the  other  having 
twice  the  number  of  teeth,  its  lead  will  be 
twice  as  great  and  its  pitch  diameter  twice 
that  of  the  other. 

(9)  Diameters  being  equal,  double  the 
number  of  teeth  indicates  one-half  the  angle 
and  vice  versa. 

(10)  If  the  angles  of  teeth  are  equal, 
either  gear  may  be  the  driver.     If  the  tooth 
angle  hi  one  gear  is  twice  that  in  another,  it 
must  be  the  driver. 


Fig.  275.     Simple  Form  of  Spiral  Gears 


The  lines  representing  the  angles 
of  the  teeth  of  spiral  gears  must  be 

tangents  to  the  side  of  the  tooth  at  the  pitch  line  and  in  the  center 
of  the  face  of  the  gear.  If  the  pitch  is  comparatively  large  in 
proportion  to  the  diameter  of  the  pitch  circle,  the  angle  will  be  con- 
siderably less  at  the  bottom  of  the  tooth  than  on  the  pitch  line,  and 
considerably  greater  at  the  points  of  the  teeth. 

The  simplest  form  of  spiral  gears  is  shown  in  Fig.  275,  in  which 
the  shafts  are  parallel  and  the  teeth  of  both  gears  are  cut  at  an  angle 


MACHINE  SHOP  WORK 


213 


of  30  degrees  to  their  axes.  This  angle  is  not  arbitrary,  as  any  angle 
that  permits  the  teeth  to  engage  properly  is  admissible.  It  should  not 
exceed  45  degrees.  The  two  gears  may  have  relatively  any  number 
of  teeth,  the  same  as  spur  gears.  Gears  of  this  form  are  frequently 
called  helical,  in  consequence  of  their  spiral  form  of  teeth  resembling 
the  helix.  This  is  the  customary  angle  for  such  gears.  Their  action 
is  similar  to  that  of  ordinary  spur  gears;  but  in  consequence  of  the 
progressive  engagement  of  the  teeth,  they  will  run  with  less  noise 


Fig.  276.     Spiral  Gears  Whose  Shafts  Are  at  Right  Angles 

and  shock,  even  when  running  at  high  speeds  or  when  transmitting 
heavy  loads. 

Fig.  276  represents  a  pair  of  spiral  gears  whose  shafts  are  at 
right  angles  to  each  other,  and  in  which  gear  A  has  8  teeth  and  the 
gear  B  has  16  teeth.  Gear  A  is  the  driver;  and  from  the  fact  that  it 
has  but  one-half  the  number  of  teeth  of  the  gear  B,  its  speed  must 
be  twice  as  great.  The  angle  of  the  teeth  of  gear  A  is  26  degrees 
40  minutes.  As  the  shafts  stand  at  an  angle  of  90  degrees,  we 
subtract  the  angle  of  the  teeth  of  the  gear  A  from  90  to  obtain  the 
angle  of  the  teeth  of  the  gear  B,  giving  63  degrees  20  minutes. 
The  sum  of  the  two  angles  equals  the  angle  of  the  two  shafts.  That 
spiral  gearing  and  worm  gearing  are  closely  allied  is  evident  from 


214  MACHINE  SHOP  WORK 

this  example.  In  analyzing  the  action  of  these  devices,  this  fact 
should  not  be  forgotten. 

The  necessary  calculations  for  designing  a  pair  of  spiral  gears 
may  be  illustrated  by  the  following  example :  The  gears  are  to  be  4 
and  16  inches  diameter  of  pitch  circle,  and  the  shafts  are  parallel. 
The  larger  will  have  a  lead  of  96  inches;  therefore  the  smaller  will 
have  a  lead  in  the  same  ratio  as  the  diameters,  or  24  inches.  Taking 
the  large  gear,  16X3.1416  =  50.2656  circumference,  which,  divided  by 
the  lead  (96),  gives  .5235.  Consulting  a  table  of  natural  tangents, 
we  find  that  this  amount  represents  an  angle  of  27  degrees  40  min- 
utes. The  angle  of  the  smaller  gear  will  be  the  same. 

If  shafts  are  at  other  than  right  angles,  this  condition  will 
change  the  angles  of  the  teeth  of  spiral  gears;  and  when  the  pitch 
diameters  are  alike  and  the  numbers  of  teeth  different,  the  angles 
will  be  different. 

It  is  customary  to  use  racks  in  connection  with  spiral  gears,  the 
gear  being  of  comparatively  short  lead.  This  device  is  practically 
the  screw  and  nut,  the  spiral  gear  acting  as  the  screw  and  the  rack  as 
the  nut.  In  designing  racks  for  this  purpose  the  teeth  may  be  at 
right  angles  to  the  line  of  movement  or  at  any  angle  between  this 
position  and  45  degrees.  The  shaft  of  the  spiral  gear  used  with  a 
rack  may  be  at  any  angle  from  parallel  to  the  line  of  motion  to  45 
degrees.  Angles  of  35  degrees  or  less  will  produce  better  results 
under  usual  conditions.  The  pitch  of  the  spiral,  the  number  of 
teeth,  and  the  angle  of  the  shaft  will  govern  the  angle  of  the  teeth 
of  the  rack.  The  teeth  of  the  rack  may  be  of  concave  form,  similar 
to  those  of  the  worm  gear  if  a  large  area  of  contact  is  required  for 
heavy  work.  Otherwise  they  are  usually  cut  in  a  straight  line. 
The  form  of  the  teeth  should  be  with  straight  lines  for  the  side  of 
the  teeth,  inclined  14J  degrees. 

GEAR  CUTTING  PROCESSES 

Two  general  processes  are  used  for  cutting  the  teeth  of  gears: 
milling  and  planing.  Either  of  these  processes  may  be  used  for 
cutting  the  teeth  of  spur  gears,  bevel  gears,  internal  gears,  racks, 
etc.,  but  they  are  not  equally  adapted  for  spiral  gears  or  worm  gears. 

Milling  Process.  The  first  process,  milling  with  a  properly 
formed  revolving  cutter,  as  in  ordinary  milling  machine  work,  is 


MACHINE  SHOP  WORK  215 

applicable  not  only  to  the  work  mentioned  above,  but  also  to  the 
cutting  of  spiral  gears  and  a  portion  of  the  work  upon  worm  gears. 
The  cutter  must  be  shaped  exactly  to  the  form  of  the  space  between 
the  teeth  of  the  gear  to  be  cut.  It  must  revolve  at  a  speed  suitable 
to  the  kind  of  metal  to  be  cut,  and  must  be  supported  by  a  spindle 
of  ample  dimensions  properly  supported  in  well-fitting  journal 
boxes,  set  in  housings  of  such  dimensions  and  weight  as  to  insure 
rigidity  and  the  elimination  of  vibration.  The  work  to  be  cut  must 
be  properly  mounted  so  as  to  avoid  vibration  as  much  as  possible, 
and  be  provided  with  feeding  mechanism  by  which  a  rate  of  feed 
may  be  produced  according  to  the  speed  of  the  cutter  and  the  kind 
of  metal  to  be  cut. 

For  ordinary  uses  this  process  produces  satisfactory  results  upon 
spur  gears,  internal  gears,  and  racks.  While  it  is  used  also  for  much 
bevel  gear  work  and  answers  the  requirements  of  ordinary  work, 
there  are  conditions  in  the  form  of  teeth  of  bevel  gears  that  do  not 
exist  in  that  of  spur  gears.  It  has  been  previously  explained  that  the 
dimensions  of  the  tooth  parts  of  a  bevel  gear  are  measured  at 
the  outer  end,  or  at  the  largest  part  of  the  tooth,  while  the  lines  of  the 
tooth  are  radial,  meeting  at  the  apex  of  the  cone  base,  from  which 
the  gear  takes  its  form.  It  may  therefore  be  readily  understood 
that  it  is  quite  impossible  to  form  a  revolving  cutter  so  as  to  cut  to 
the  correct  theoretical  dimensions  of  the  tooth  through  its  entire 
length.  It  is  the  practice  to  form  the  contour  of  the  cutter  so  that 
it  is  a  compromise  between  the  correct  forms  of  the  two  ends  of  the 
teeth,  but  rather  closer  to  the  form  at  the  outer  or  larger  end, 
the  form  being  practically  correct  at  a  point  one-third  of  the  face  of  the 
tooth  from  its  outer  end.  As  a  rule,  the  width  of  face  of  a  bevel 
gear  should  not  be  over  five  times  the  thickness  of  the  teeth  at  the 
outer  end.  It  is  usually  considerably  less.  If  the  face  is  too  wide, 
the  inner  ends  of  the  teeth  will  be  cut  away  too  much  as  the  width 
of  the  cut  is  uniform  from  one  end  to  the  other;  and  this  results  in 
thin  and  useless  teeth  for  a  considerable  part  of  their  length 
from  the  inner  end,  as  there  is  no  contact  with  or  bearing  upon 
the  teeth  of  the  engaging  gear  at  this  point.  For  this  reason, 
resort  is  had  to  filing  the  faces  of  the  teeth  at  the  large  end, 
after  the  gears  have  been  run  together  so  as  to  show  by  the  marks 
thus  produced. 


216  MACHINE  SHOP  WORK 

Planing  Process.  First  Method.  The  second  process,  that  of 
planing  the  forms  of  the  teeth,  is  accomplished  by  three  methods. 
One  is  to  form  a  planing  tool  to  the  exact  contour  of  the  space  between 
the  teeth,  and  by  successive  strokes  of  any  machine  having  a  recip- 
rocating ram  to  carry  the  tool,  some  fixture  for  holding  the  gear 
blank,  and  a  device  for  indexing  the  tooth  spaces.  This  work  is 
frequently  done  on  a  shaper  and  sometimes  on  a  planer.  This 
method  produces  a  cut  writh  parallel  sides  the  same  as  a  revolving 
cutter,  and  the  depth  of  the  cut  may  be  varied  at  the  two  ends  so 
as  to  be  adaptable  to  bevel  gear  wrork  although  producing  work  that 
is  no  more  theoretically  correct  than  that  of  the  revolving  cutter. 
This  device  may  be  used  upon  spur  gears,  internal  gears,  racks,  etc., 

with  fairly  good  effect, 
Iput  is  a  comparatively 
slow  process.  It  may, 
however,  be  sometimes 
used  where  a  milling 
machine  or  ordinary 
gear  cutter  cannot,  as 
in  cutting  the  teeth  of 
internal  gears. 

Second  Method.  The 

Planing  Gear  Teeth 

second  method,  of  plan- 
ing gear  teeth — which  has  proven  an  important  device  for  forming 
the  teeth  of  spur  gears,  internal  gears,  and  racks — operates  by  means 
of  a  circular  cutter  upon  which  the  teeth  are  formed  similar  to  the 
teeth  of  the  gear  itself.  This  is  the  system  used  in  the  Fellows 
gear  shaper.  The  action  of  the  cutter  is  shown  in  Fig.  277.  The 
gear  blank  is  mounted  on  a  proper  spindle,  and  the  machine  started, 
the  cutter  reciprocating  on  its  center  line  and  parallel  to  its  axis. 
The  cutter  is  then  fed  toward  the  blank,  and  cuts  its  wTay  to  the 
proper  depth.  At  this  point,  both  the  cutter  and  the  blank  begin 
to  rotate  in  the  directions  indicated  by  the  arrows,  the  cutter  main- 
taining its  reciprocating  motion.  This  rotation  of  the  cutter  and 
the  blank  is  obtained  by  separate  and  external  mechanism,  which 
insures  that  the  movement  shall  be  the  same  as  though  the  cutter 
and  the  blank  were  two  complete  gears  in  correct  mesh.  The  com- 
bined result  of  rotary  and  reciprocating  motions  is  that  the  cutter 


MACHINE  SHOP  WORK  217 

teeth  generate  conjugate  teeth  in  the  blank,  which  mesh  correctly 
with  the  cutter  teeth  and  with  one  another.  Any  two  gears  of  the 
same  pitch  cut  with  this  cutter  will  mesh  correctly  together. 

Third  Method.  A  third  method  of  planing  gear  teeth,  and  one 
of  very  great  importance,  particularly  in  forming  the  teeth  of  bevel 
gears,  is  used  by  various  gear-cutting  machine  builders.  In  some 
cases  the  tool  slide  travels  upon  a  carriage  whereof  one  end  is  pivoted 
directly  under  the  apex  of  the  base  cone,  and  its  opposite  or  outer 
end  is  properly  guided  to  the  exact  contour  of  the  tooth,  which  is 
formed  by  a  tool  having  a  single  cutting  edge  with  a  narrow  and 
somewhat  rounded  cutting  point.  In  other  cases  the  tool  slide  is  in 
a  fixed  plane,  while  the  arbor  upon  which  the  gear  blank  is  mounted 
is  journaled  in  a  portion  of  the 
machine  so  constructed  as  to  give 
the  necessary  '  adjustment  and 
movements  to  the  gear  blank. 
These  planing  processes  will  be 
more  particularly  noticed  later  in 
describing  the  various  types  of 
gear-cutting  machines. 

Mobbing  Gears.    In  forming 
the  teeth  of  worm  gears,  the  greater 

part    Of  the  Space  1S  CUt  OUt  by  a  Fig.278.     Hob  for  Forming  Teeth  of 

stocking  cutter  or  roughing  cutter, 

which  is  adjusted  at  a  proper  angle,  according  to  the  pitch  of  the 
worm  which  the  worm  gear  is  to  fit,  and  gradually  sunk  into  the  face 
of  the  worm-gear  blank  so  as  to  form  the  spaces  between  the  teeth. 
This  revolving  cutter  will  not  produce  the  correct  form  for  the  teeth, 
as  they  must  fit  the  sides  of  the  worm  thread.  "  Recourse  is  therefore 
had  to  a  cutter  called  a  hob,  which  is  shown  in  Fig.  278.  This  cutter 
is  in  effect  a  worm,  across  the  threads  of  which  are  formed  deep 
grooves,  thereby  producing  cutting  faces  as  shown  in  the  engraving. 
Each  of  the  teeth  shown  is  relieved,  or  backed  off,  so  that  when  the 
faces  of  the  teeth  become  dulled  by  use  and  are  ground,  the  accurate 
form  of  the  teeth  is  not  changed.  This  hob  is  mounted  in  the  exact 
position  that  the  worm*  is  to  take  with  reference  to  the  worm  gear, 
except  that  the  centers  of  the  spindle  carrying  the  hob,  and  the  arbor 
carrying  the  worm  gear,  are  slightly  farther  apart,  and  so  arranged 


218 


MACHINE  SHOP  WORK 


as  to  be  brought  to  the  exact  distance  apart,  as  the  hob  shapes  the 
teeth  of  the  worm  gear.  This  operation,  called  hobbing,  is  per- 
formed by  the  rotation  of  the  hob,  which,  acting  as  a  screw  and 
producing  the  rotation  of  the  worm  gear,  forms  the  teeth  by  its 
cutting  action.  In  some  cases  the  worm  gear  is  positively  rotated 
by  suitable  gearing.  Previous  gashing  is  then  unnecessary. 

In  Fig.  279  is  shown  the  usual  form  of  a  rotating  cutter  for  pro- 
ducing the  involute  form  of  gear  teeth.  The  teeth  of  these  cutters 

are  relieved,  or  backed  off,  so  that 
their  form  is  not  changed  when 
ground  upon  the  face  after  they  have 
become  dulled  by  use. 

Tools  for  Testing  Gear  Teeth. 
To  ascertain  if  the  teeth  of  a  gear 
are  being  cut  properly,  the  gear- 
tooth  caliper  shown  in  Fig.  280  is 
used.  This  is  for  measuring  the  dis- 
tance from  the  top  of  the  teeth  to  the 
pitch  line,  and  the  thickness  of  the 
teeth  at  the  pitch  line.  It  will  meas- 
ure all  teeth  from  2  to  20  diametral 
pitch,  and  is  provided  with  vernier 
scales  in  both  directions  so  that  it 
can  be  very  accurately  adjusted  to 
the  required  dimensions  as  given  in 
Table  X. 

Fixed  gages  are  frequently  used 

instead  of  the  gear-tooth  caliper.  Thus,  for  the  depth  of  the  teeth, 
a  sheet-metal  g~ge  df  the  form  shown  in  Fig.  281  is  provided.  A 
gage  for  the  width  of  the  teeth  is  shown  in  Fig.  282.  There  must 
be  separate  gages  for  each  different  pitch,  each  of  which  is  stamped 
with  a  figure  indicating  the  pitch  for  which  it  is  to  be  used. 

General  Conditions  of  Practical  Gear  Cutting.  Before  describ- 
ing the  various  types  of  gear-cutting  machines  and  the  methods  by 
which  each  performs  its  work,  attention  is  directed  to  some  of  the 
general  conditions  in  the  practical  use  of  gear-cutting  machines  of 
any  type. 

When  rotating  cutters  are  used,  they  are  mounted  upon  the 


Fig.  279. 


Rotating  Cutter  for  Involute 
Teeth 


MACHINE  SHOP  WORK 


219 


spindle  and  secured  in  place  in  the  same  manner  as  ordinary  milling- 
machine  cutters — namely,  located  in  proper  position  by  clamp  collars 


Fig.  280.     Gear-Tooth  Caliper  in  Use 

on  each  side,  held  in  place  by  a  nut.  Care  should  be  taken  to  see 
that  they  run  true.  If  not,  there  is  liable  to  be  dirt  or  chips  between 
the  collars  and  shoulders  of  the  arbor  or  the  cutter;  and  they  should 
be  removed,  carefully 
cleaned,  and  replaced. 
If  still  out  of  true,  the 
arbor  may  be  sprung, 
and  it  should  be  cor- 
rected before  any  work 
is  done.  The  cutters 
should  be  sharp;  other- 
wise much  heat  and 
friction  will  be  caused, 
and  poor  and  inefficient 
work  will  result. 

The  gear  blank  is 

„  .  Fig.  281.     Sheet-Metal  Gage  for  Measuring  Depth  of  Teeth 

usually  mounted  upon 

an  arbor  fitting  in  a  taper-reamed  hole  in  the  index  spindle,  and 
sometimes  reaches  entirely  through  the  spindle,  being  confined  in 
position  by  a  nut  in  its  rear  end.  These  arbors  are  of  different 


220 


MACHINE  SHOP  WORK 


diameters  so  as  to  fit  all  the  regular  sizes  of  the  bore  of  the  gear 
blanks.  The  gear  blank  is  adjusted  to  its  proper  place  on  the  arbor 
by  loose  collars  if  necessary,  and  confined  by  a  nut  which  must  be 
screwed  up  very  tightly  so  as  to  prevent  the  blank  from  moving 
on  the  arbor  during  the  process  of  the  cutting. 

Upon  the  cutter  shown  in  Fig.  279  is  a  line  A,  exactly  in  the 
center  of  the  tooth.  The  position  of  the  cutter  and  the  work  arbor 
carrying  the  gear  blank  must  be  so  adjusted  with  relation  to  each 
other  that  this  line  will  exactly  coincide  with  the  axis  of  the  arbor. 
To  effect  this,  in  machines  in  which  the  work  arbor  is  horizontal,  it  is 
brought  under  the  cutter  and  accurately  adjusted;  then  the  arbor 

and  its  carriage  are  moved 
to  the  proper  position  to  be- 
gin cutting  the  teeth.  On  some 
machines,  special  provision  is 
made  for  centering  the  cutter. 
The  proper  change  gears 
or  such  similar  devices  as  the 
machine  is  provided  with  are 
then  arranged  for  the  spacing 
or  indexing  of  the  blank.  The 
design  of  this  device  may  vary 
in  different  machines,  but  the 
device  usually  consists  of  or- 
dinary change  gears,  which  are  selected  and  applied  according  to 
a  table  furnished  with  the  machine,  which  table  gives  the  required 
gears  for  all  the  usual  numbers  of  teeth  to  be  cut.  The  machine  is 
started,  and  the  work  brought  to  the  cutter  so  as  to  mark  it  plainly, 
when  it  is  withdrawn  and  the  machine  stopped.  The  indexing  device 
is  now  operated,  step  by  step,  through  one  entire  revolution  of  the 
gear  blank,  back  to  the  mark  made  by  the  cutter.  The  work  is 
now  brought  up  to  the  cutter  to  ascertain  if  it  exactly  coincides 
with  the  mark  made.  If  so,  the  cutter  may  be  set  to  the  proper 
depth  by  advancing  it  to  a  point  considerably  less  than  the  whole 
depth,  and  cutting  down  slightly  past  the  center  of  the  cutter; 
then  moving  the  cutter,  in  the  line  of  its  feed,  out  of  the  cut,  and 
measuring  the  depth.  The  work  is  now  slightly  advanced  and 
the  cut  deepened;  and  so  on,  until  the  proper  depth  is  reached. 


Fig.  282.     Sheet-Metal  Gage  for  Measuring 
Width  of  Teeth 


MACHINE  SHOP  WORK  221 

On  some  machines  an  index  is  .provided  on  the  adjusting  screw, 
enabling  the  work  to  be  brought  up  to  the  cutter  so  as  to  barely 
touch  it;  and  then,  by  reading  the  index,  the  entire  depth  is  adjusted 
at  once  and  with  certainty. 

When  gears  of  very  coarse  pitch — as  2  J  pitch  and  larger  made  of 
cast  iron,  and  5  pitch  and  larger  made  of  steel — are  to  be  cut.  it  is 
customary  to  use  first  a  roughing  or  stocking  cutter  which  removes 
two-thirds  or  more  of  the  metal,  after  which  the  finishing  cutter, 
shown  in  Fig.  279,  is  used  to  finish  the  work.  A  roughing  cutter 
usually  has  inclined,  straight,  or  stepped  sides,  no  attempt  being 
made  to  follow  the  contour  of  the  finished  tooth. 

Speed  of  Cutters.  On  gear  work  the  speed  of  cutters  will  be 
slightly  less  than  that  of  the  ordinary  milling  cutters,  as  the  cutting 
surface  is  not  only  over  the  points  of  the  cutting  teeth,  but  upon 
both  sides.  Hence  the  speed  will  more  nearly  approach  the  proper 
speed  for  the  formed  cutters  of  the  milling  machine.  The  variations 
of  speed  for  the  different  kinds  of  material  will  be  the  same  as  for 
milling-machine  cutters. 

Feed.  The  proper  feed  for  gear  cutting  will  be  the  same  as  for 
milling-machine  cutters  (or  in  some  cases  slightly  less),  on  the  same 
material,  for  cast  iron  usually  about  ^  inch  per  revolution. 

Cutting  Spiral  Gears.  In  cutting  spiral  gears  the  universal 
milling  machine  is  generally  used,  as  it  is  provided  with  proper 
devices  for  rotating  the  gear  blank  at  the  same  time  that  it  is  fed 
toward  the  cutter.  The  machine  is  provided  with  an  indexing 
mechanism,  and  also  with  change  gears  by  which  any  length  of  lead 
of  the  spiral  may  be  obtained.  In  all  cases  of  spiral  gear  cutting, 
the  milling-machine  table  must  be  set  at  an  angle,  as  shown  in 
Fig.  276,  the  center  of  the  cutter  being  directly  above  the  point  of 
intersection  of  the  axes  of  the  arbor  carrying  the  gear  blank  and  that 
upon  which  the  cutter  is  mounted. 

The  preliminary  cutting  or  gashing  of  worm  gears  is  frequently 
done  on  a  universal  milling  machine,  on  account  of  its  adaptability 
to  all  kinds  of  angular  work  and  to  making  feeds  in  all  directions. 

Lubrication  of  Cutters.  In  gear  cutting,  the  lubrication  of 
cutters  is  governed  by  the  same  conditions  and  requirements  as  in 
ordinary  milling-machine  work,  and  is  governed  by  the  material  to 
be  cut. 


222 


MACHINE  SHOP  WORK 


TYPES  OF  GEAR-CUTTING  MACHINES 

To  familiarize  the  student  with  the  special  features  of  different 
types  of  gear-cutting  machines,  illustrations  and  descriptions  are 
given  of  the  machines  made  by  some  of  the  more  prominent  builders. 

Whiton  Gear=Cutting  Machine.  In  Fig.  283  is  shown  the 
Whiton  automatic  gear-cutting  machine.  The  cutter  is  carried  by 


Fig.  283.     Automatic  Gear-Cutting  Machine 
Courtesy  of  D.  E.  Whiton  Machine  Company,  New  London,  Connecticut 

the  spindle  A,  which  is  journaled  in  a  saddle  B,  sliding  upon  the 
swinging  carriage  C  and  capable  of  adjustment  at  any  angle  neces- 
sary to  cut  bevel  gears.  The  machine  is  shown  arranged  for  cutting 
spur  gears.  The  cutter  arbor  A  is  driven  by  the  pulley  D  at  the 
back  of  the  machine,  acting  through  a  system  of  gears  not  shown. 
The  blank  to  be  cut  is  held  on  an  arbor  fitted  into  the  vertical  spindle 
E,  and  its  upper  end  supported  by  a  center  in  the  arm,  adjustably 


MACHINE  SHOP  WORK 


223 


clamped  to  the  column  G.  The  traversing  screw  H,  has  a  graduated 
dial.  A  gage  is  provided  for  centering  the  cutter;  and  graduated 
stops  provide  micrometer  adjustments  for  setting  over  the  cutter 
in  bevel  gear  cutting,  and  for  setting  over  the  blank.  At  J  are  the 
change  gears  of  the  indexing  mechanism. 

Brown  and  Sharpe  Gear=Cutting  Machine.    Fig.  284  repre- 
sents a  Brown  and  Sharpe  gear-cutting  machine.    The  gear  blank  is 


Fig.  284.     Number  6  Gear-Cutting  Machine 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  Island 

carried  on  an  arbor  fitted  to  the  horizontal  spindle  A,  and  supported 
by  the  outer  supporting  bracket  B.  The  indexing  mechanism  is  in 
the  rear  of  the  indexing  wheel  C.  The  cutter  is  carried  by  the  cutter 
spindle  D,  mounted  in  the  traveling  carriage  E.  In  smaller  machines 
the  base  upon  which  this  carriage  slides  is  pivoted  so  as  to  be 
set  at  any  required  angle  for  cutting  bevel  gears.  The  machine  is 


224 


MACHINE  SHOP  WORK 


entirely  automatic  in  its  action.     It  has  an  attachment  for  cutting 
internal  gears. 

Automatic  Qear=Cutting  Machine.  The  automatic  gear-cutting 
machine  built  by  Gould  and  Eberhardt  is  shown  in  Fig.  285.  It  is 
of  the  same  type  as  that  built  by  Brown  and  Sharpe  and  possesses 
some  excellent  features.  The  gear  blank  and  cutter  are  mounted  in 
a  similar  manner,  and  the  adjustments  are  made  at  much  the  same 
points.  It  is  furnished  with  attachments  for  hobbing  worm  gears 


Fig.  285.     "New  Type"  Gear-Cutting  Machine  Entirely  Automatic  for  Cutting  Spur  Gears  Only 
Courtesy  of  Goidd  and  Eberhardt,  Newark,  New  Jersey 

and  for  cutting  racks  and  internal  gears.    The  one  shown  is  not 
adapted  for  cutting  bevel  gears. 

Becker  Qear=Cutting  Machine.  The  Becker  Milling  Company 
gear-cutting  machine,  shown  in  Fig.  286  is  of  the  milling-machine 
type,  designed  by  Amos  H.  Brainard,  a  builder  of  milling  machines. 
The  gear  blank  is  mounted  upon  an  arbor  fitting  a  taper  hole  in 
the  work  spindle  A  or  fixed  upon  an  arbor  and  mounted  on  centers. 
The  cutter  is  mounted  upon  a  cutter  arbor  B,  journaled  in  a  sliding 
saddle  C  whose  support  D  is  pivoted  to  the  machine  knee  so  as  to  be 


MACHINE  SHOP  WORK  225 

adjustable  to  any  angle  required  for  cutting  bevel  gears  as  well  as 
spur  gears.    The  machine  is  entirely  automatic  in  its  action. 

Bench  Gear=Cutting  Machine,*  Fig.  287  shows  a  bench  gear- 
cutting  machine  built  by  the  Sloan  and  Chase  Manufacturing  Com- 
pany. It  is  intended  for  small  gears  only,  and  will  not  cut  a  gear 
larger  than  3|  inches  in  diameter.  The  same  company  build  large 
machines,  some  of  the  Brainard  type.  The  machine  shown  carries  the 


.  236.     Gear  Cutter 
Courtesy  of  Becker  Milling  Machine  Company,  Hyde  Park,  Massachusetts 

gear  blank  on  the  spindle  A,  and  the  cutter  on  the  spindle  B.  The 
indexing  mechanism  is  at  C,  and  the  machine  is  entirely  automatic. 
Fellows  Gear  Shaper.  The  Fellows  gear  shaper,  shown  in 
Fig.  288,  is  a  distinct  type  in  construction  and  action,  the  peculiar 
form  of  cutter  used  being  shown  in  Fig.  277.  The  gear  blank  is 
mounted  on  the  vertical  work  spindle  A,  which  has  on  its  lower  end 
and  within  the  casing  B  an  indexing  worm  gear  operated  by  the 
change  gears  at  C.  These  are  driven  from  the  cone  pulley  D  by 
means  of  the  vertical  shaft  E,  by  a  very  gradual  but  continuous 


226 


MACHINE  SHOP  WORK 


motion  as  the  vertically  reciprocating  cutter  F  forms  the  teeth  on 
the  blank,  gradually  rotating  in  unison  with  the  rotation  of  the  blank. 
The  reciprocating  movement  of  the  ram  carrying  the  cutter  is  pro- 
duced by  suitable  mechanism  within  the  casing  H  operated  by  the 
shaft  G.  The  machine  is  automatic  in  its  action,  and  cuts  spur  gears 
and  internal  gears.  A  modified  form  machine  is  adapted  to  cutting 
the  teeth  of  racks.  The  cutting  action  is  that  of  planing. 

Gleason  Gear  Planer.    In  Fig.  289  is  shown  the  Gleason  gear 
planer   which  is  an  excellently  designed  machine  for  planing  gear 


Fig.  287.     Bench  Gear  Cutter 
Courtesy  of  Sloan  and  Chase  Manufacturing  Company 

teeth  with  a  single  tool  having  a  narrow,  rounded  cutting  point. 
The  gear  blank  A  is  mounted  on  a  horizontal  spindle  having  at  its 
rear  end  suitable  automatic  indexing  mechanism  B.  The  tool  C  is 
carried  in  a  reciprocating  tool  block  D,  which  travels  upon  a  swing- 
ing carriage  pivoted  at  E  directly  under  the  apex  of  the  base  cone  of 
the  gear  blank.  The  exact  curve  and  direction  of  its  feed  are  con- 
trolled by  one  of  the  formers  F,  G,  H,  mounted  upon  the  triangular 
former  carrier  J,  which  may  be  rotated  so  as  to  bring  either  former 
up  to  its  operative  position,  forming  a  rest  and  guide  for  the  friction 
roller  K  on  the  outer  end  of  the  swinging  carriage.  Of  the  three 


MACHINE  SHOP  WORK 


227 


formers,  F  is  used  for  a  roughing  cut,  and  the  other  two  for  the  upper 
and  under  sides  of  the  tooth.  Being  placed  at  a  considerable  distance 
from  the  pivot  upon  which  the  carriage  swings,  they  are  made  many 
times  larger  than  the  tooth,  and  great  accuracy  of  form  is  thereby 
secured.  The  roughing  cut  is  frequently  made  with  a  rotating  cutter 


Fig.  288.     Gear  Shaper 
Courtesy  of  Fellows  Gear  Shaper  Company,  Springfield,  Vermont 

on  an  ordinary  gear  cutting  machine.  Modifications  of  this  machine 
are  built  specially  for  cutting  spur  gears  upon  the  same  principle. 

Bilgram  Qear=Planing  Machine.  The  Bilgram  gear-planing 
machine,  shown  in  Fig.  290,  operates  upon  a  principle  similar  to  that 
of  the  machine  just  described,  but  with  this  important  difference. 
In  the  Gleason  machine  the  tool  is  caused  to  move  so  as  to  trace  the 
exact  contour  of  the  side  of  the  gear  tooth,  in  addition  to  its  recipro- 


222 


MACHINE  SHOP  WORK 


eating  movement  for  cutting.     In  the  Bilgram  machine,  on  the  other 
hand,  the  tool  ha?  only  a  reciprocating  motion,  while  the  gear  blank 


Fig.  289.     Gear  Planer 
Courtesy  of  Gleason  Tool  Company,  Rochester,  New  York 


Fig.  290.     Gear-Planing  Machine 


and  its  supporting  mechanism  are  given  the  rolling  motion  similar 
to  that  imparted  by  one  rotating  gear  to  another,  or  that  of  a  rolling 


MACHINE  SHOP  WORK  229 

cone.  To  accomplish  this,  the  axis  must  in  the  first  place  be  moved 
in  the  manner  of  a  conical  pendulum.  Therefore  the  bearing  of  the 
arbor  which  carries  the  blank  is  secured  in  an  inclined  position 
between  two  uprights  to  a  semicircular  horizontal  plate,  which  can  be 
oscillated  on  a  vertical  axis  passing  through  the  apex  of  the  base  cone 
of  the  blank.  To  complete  the  rolling  action,  the  arbor  must  in  the 
second  place  receive  simultaneously  the  proper  rotation;  and  this 
effect  is  produced  in  the  machine  by  having  a  portion  of  a  cone 
(corresponding  with  the  pitch  cone  of  the  blank)  attached  to  the 
arbor,  and  held  by  two  flexible  steel  bands  stretched  in  opposite 
directions,  one  end  being  attached  to  the  cone  and  the  other  to  a 
fixed  part  of  the  mechanism,  thus  preventing  this  cone  from  making 
any  but  a  rolling  motion  when  the  arbor  receives  the  conical  swinging^ 
motion.  In  the  engraving  A  is  the  blank  to  be  cut;  B  the  ram 
carrying  the  cutting  tool;  and  C  the  indexing  and  rolling  mechanism. 

TURRET  LATHES 

The  turret  lathe,  as  we  know  it  today,  is  a  comparatively  modern 
machine,  and  was  developed  from  an  ordinary  engine  lathe  by  the 
addition  of  revolving  tool-holding  devices  called  turrets. 

The  turret  was  at  first  made  of  circular  form,  and  rotated  upon 
a  vertical  pivot  which  had  a  binding  nut  whereby  it  could  be  held  in 
any  desired  position.  The  circumference  of  the  circular  turret  was 
drilled  and  reamed  for  four  tools  projecting  horizontally  from  it  at 
angles  of  90  degrees  with  each  other.  Later  the  number  of  tool  holes 
was  increased  to  six,  and  the  turret  was  frequently  made  of  hex- 
agonal form. 

The  turret  was  at  first  located  upon  a  lathe  carriage  in  place  of 
the  tool  block,  and  properly  set  in  line  with  the  lathe  center  by  means 
of  the  cross-feed  screw.  The  lateral  feed,  upon  which  the  device 
depends  for  its  action,  was  obtained  by  the  operation  of  the  feeding 
mechanism  in  the  apron  attached  to  the  carriage. 

The  object  sought  to  be  accomplished  by  the  addition  of  this 
device  to  the  lathe  was  that  of  carrying  various  drilling,  reaming, 
counterboring,  and  similar  tools  by  which  several  operations  could  be 
performed  upon  a  piece  ot  work  without  removing  it  J:'rom  the  chuck, 
or_without  any  further  change  of  tools  than  that  of  revolving  'tfie 
turret.  The  tools,  when  once  adjusted,  required  no  further  altera- 


230 


MACHINE  SHOP  WORK 


tion  as  the  several  pieces  of  work  were  completed  and  removed  from 
the  chuck,  and  other  pieces  substituted  for  a  like  series  of  operations. 
By  this  means  the  work  could  be  performed  much  more  rapidly,  the 
producing  value  of  the  machine  being  correspondingly  increased. 

Fig.  291  shows  the  original  form  of  the  turret  A,  supported  upon 
the  sliding  block  B.  The  turret  is  pivoted  upon  the  vertical  stud  C, 
and  secured  in  any  desired  position  by  the  nut.  A  later  development 
provided  means  for  locating  it  positively  in  as  many  positions  as 


Fig.  291.     Original  Form  of  Turret 

there  were  holes  for  tools.  This  turret  is  drilled  for  four  tools,  three 
of  which  are  shown  at  EEE  secured  by  the  set  screws  eee. 

As  the  value  of  the  turret  mechanism  came  to  be  generally  appre- 
ciated, it  was  still  further  developed  by  the  addition  to  the  number  of 
tools  that  it  would  carry;  by  a  ratchet  arrangement  for  revolving  it; 
by  an  index  plate  for  holding  it  in  any  desired  position;  and  by  vari- 
ous other  improvements  that  will  presently  be  referred  to. 

These  developments  soon  carried  it  beyond  the  scope  of  the 
engine  lathe,  and  special  lathes  were  designed  in  which  the  improved 
turret  was  the  principal  feature.  These  are  the  turret  lathes 
proper,  as  we  find  them  built  today. 

Classification  of  Turret  Lathes.  To  obtain  a  comprehensive 
view  of  the  various  forms  of  turret  lathes,  including  engine  lathes  so 


MACHINE  SHOP  WORK  231 

modified  as  to  adapt  them  to  turret-lathe  work,  they  may  be  divided 
into  five  classes  as  follows: 

(1)  Engine  lathes  adapted  to  serve  as  turret  lathes  by  having  a  hand- 
revolved  turret  mounted  upon  the  carriage  in  place  of  the  usual  tool-block  or 
compound  rest. 

(2)  Engine  lathes  adapted  to  serve  as  turret  lathes  by  having  a  hand- 
revolved  turret  mounted  upon  a  laterally  moving  slide,  supported  upon  3,  shoe 
or  saddle  fitting  the  V'a  of  the  bed. 

(3)  The  turret  lathe  proper,  specially  designed  and  built  as  such,  with 
a  turret  revolved  and  fed  by  hand,  supported  by  and  pivoted  upon  a  slide, 
which  is  in  turn  supported  by  a  shoe  or  saddle  fitted  to  the  V'a  of  the  bed. 

(4)  A  turret  lathe  designed  and  built  in  a  similar  manner  to  that  last 
described,  and  in  which  there  is  a  power  feed  for  the  cuts.     It  is  so  arranged 
that  the  turret  is  revolved  automatically.     This  lathe  is  frequently  called  a 
semi-automatic  turret  lathe. 

(5)  A  complete  automatic  turret  lathe  having  a  power  feed  for  the  cuts; 
a  quick  return  of  the  turret  slide,  operated  by  power;  with  the  turret  automatically 
revolved  at  the  end  of  its  run. 

The  lathes  described  in  the  third,  fourth,  and  fifth  classes  are 
usually  provided  with  a  carriage  called  a  cross-slide,  carrying  one 
cutting  tool  in  front  and  frequently  another  tool  at  the  back,  inverted 
so  as  to  cut  without  reversing  the  direction  of  revolution  of  the  work. 

A  very  useful  modification  of  the  type  described  in  the  third  class 
is  called  the  monitor  lathe,  probably  from  the  fancied  resemblance  of 
its  turret  to  the  turret  of  the  type  of  warship  called  a  "monitor".  In 
this  lathe  the  slide  upon  which  the  turret  is  supported  and  pivoted 
is  moved  back  and  forth  by  means  of  a  horizontal  hand  lever,  and 
is  therefore  very  rapid  in  its  operation.  From  the  fact  that  this  con- 
stitutes a  rapid  hand  feed  for  the  turret,  this  type  is  adapted  for  light 
work  or  work  upon  soft  metals.  For  this  class  of  work  it  is  a  very 
rapid  and  efficient  machine.  Fig.  292  shows  one  of  these  machines. 
The  lever  A  is  for  operating  the  turret  slide  B,  carrying  the  turret 
C,  which  was  first  revolved  by  hand  but  later  by  a  ratchet  device 
located  in  its  base  and  actuated  by  a  pawl  during  the  latter  portion 
of  the  movement  of  the  slide  in  withdrawing  the  cutting  tools  from 
the  work.  The  lever  D  is  for  operating  the  cross-slide  E,  carrying  a 
cutting-off  tool  and  frequently  a  forming  tool  also. 

In  a  general  way  it  may  be  said  that  the  turret  lathe  is  one  of  the 
most  useful  and  efficient  machines  in  the  shop  for  the  production  of 
parts  in  large  (and  often  in  moderate)  quantities  usually  known  as 
repetition  work,  which  can  be  finished  by  the  operations  of  turning, 


232 


MACHINE  SHOP  WORK 


facing,  boring,  reaming,  counterboring,  or  any  similar  circular  work,  i 
the  machine  being  equipped  with  suitable  tools  for  the  work  under-  ! 
taken. 

This  machine  is  practically  identical  with  that  frequently  known  j 
as  a  hand  screw  machine,  which  has  the  wire-feed  attachment  for  • 
feeding  bars  of  stock  through  the  main  spindle.  It  is  used  for  mak-  ] 
ing  not  only  screws,  but  many  small  cylindrical  parts,  particularly  j 


Fig.  292.     Form  of  Monitor  Lathe 

when  the  quantities  of  one  kind  are  not  of  sufficient  number  to  make 
it  economical  to  set  up  the  automatic  screw  machine  for  their  manu- 
facture. The  other  machine  which  is  the  only  successful  rival  of  the 
turret  lathe  and  the  hand  machine,  is  of  the  same  family,  but  known 
as  the  "automatic  screw  machine",  which  will  be  illustrated  and 
described  later  on. 

An  engine  lathe  equipped  as  described  in  class  1  is  shown  in 
Fig.  293.    In  this  particular  machine,  the  turret  is  of  hexagonal 


MACHINE  SHOP  WORK 


233 


form.  In  the  earlier  machines  it  was  usually  cylindrical.  It  is 
arranged  to  be  revolved  by  hand,  and  is  released  or  held  in  place  as 
desired  by  a  plunger  operated  by  the  lever  A  and  engaging  in  slots 
in  the  periphery  of  a  circular  plate  attached  to  the  base  of  the  turret. 
The  transverse  position  of  the  turret  is  adjusted  by  the  cross-feed 
screw  B;  and  the  lateral  movement  or  cutting  feed  is  by  the  crank 
C,  or  by  the  power  lateral  feed  of  the  lathe.  The  turret  is  pivoted 
to  the  shoe  D,  which  is  quite  similar  to  the  one  shown  in  Fig.  291, 
and  fits  on  the  dovetail  of  the  lathe  carriage  after  the  removal  of  the 


Fig.  293.     Engine  Lathe  with  Hand-Revolved  Turret  on  Carriage  in  Place  of  Tool-Block 

regular  compound  rest  or  tool-block.      In  all  other  respects  this 
machine  is  a  regular  engine  lathe. 

Fig.  294  shows  the  machine  referred  to  in  class  2.  In  this  case 
the  tailstock  of  the  engine  lathe  is  removed,  and  replaced  by  a  base 
A  similarly  attached,  which  supports  the  turret  slide  B,  upon  which 
is  pivoted  the  turret  C.  The  base  A  is  fixed  at  any  desired  point  on 
the  lathe  bed.  The  turret  slide  B  is  operated  by  the  pilot  wheel  D, 
and  limited  in  its  forward  movement  by  the  adjusting  screw  E. 
Frequently  there  are  several  of  these  screws  in  a  sliding,  swinging,  or 
rotating  stop-holder,  by  which  device  an  adjustable  stop  may  be  pro- 
vided for  each  tool  in  the  turret.  The  regular  compound  rest  F  is 
retained  in  its  place,  and  may  be  used  to  carry  forming  or  cutting-off 


234 


MACHINE  SHOP  WORK 


MACHINE  SHOP  WORK  235 

tools.  The  lathe  proper  may  be  any  form  of  an  engine  lathe.  Nearly 
all  manufacturers  ef  engine  lathes  now  furnish  turrets  to  fit  either 
upon  the  carriage  or  upon  the  V's  of  the  bed,  for  the  purpose  of  doing 
these  classes  of  work. 

The  machine  specified  in  class  3  is  shown  in  Fig.  295.  It  is 
designed  and  built  as  a  turret  lathe.  The  base  A,  turret  slide  B, 
turret  C,  and  pilot  wheel  D  are  constructed  and  operate  as  in  the  last 
example.  The  turret  slide  A  is  provided  with  an  adjustable  multiple- 
stop  screw  E,  by  which  the  length  of  cut  of  each  individual  tool  in  the 


Tig.  295.     Turret  Lathe,  Hand-Revolved  and  Hand-Fed 
Courtesy  of  Pratt  and  Whitney  Company,  Hartford,  Connecticut 

turret  is  limited.  A  simple  form  of  cross-slide  takes  the  place  of  the 
carriage  on  the  engine  lathe.  It  is  adjustable  to  any  point  on  the  bed. 
It  carries  two  tool-blocks  which  may  be  adjusted  in  relation  to  each 
other  by  the  hand-wheel  G.  The  entire  top  slide  carrying  the  two 
tool-posts  //  II  is  operated  transversely  by  means  of  the  lever  J.  By 
this  device,  a  cutting-off  tool  may  be  carried  in  one  tool-post,  and  a 
forming  tool  in  the  other.  This  machine  is  built  in  various  sizes. 
It  is  equipped  with  chucks  for  taking  round  and  hexagonal  rods  of 
different  diameters;  and  with  much  larger  chucks  for  holding  castings 
and  drop  forgings  which  are  to  be  bored,  reamed,  turned,  faced,  or 


236 


MACHINE  SHOP  WORK 


formed.  It  is  also  provided  with  what  is  called  a  wire  feed,  by  means 
of  which  long  bars  are  automatically  passed  entirely  through  the  main 
spindle  and  chuck.  This  device  will  be  shown  and  explained  in  con- 
nection with  Screw  Machines.  Provision  is  made  for  lubricating 
the  tools  by  a  stream  of  oil  or  other  lubricant,  contained  in  the  tank 
K  beneath  the  machine,  whence  it  is  drawn  by  a  small  rotary  pump 
(not  shown  in  the  engraving)  and  forced  up  through  the  piping  L, 
from  which  it  falls  upon  the  cutting  tools. 

In  Fig.  296  is  shown  a  turret  lathe  fulfilling  the  requirements 
stated  in  class  4.  The  turret  is  mounted  in  substantially  the  same 
manner  as  in  the  last  example,  and  is  automatically  revolved  at  the 


Fig.  296.     Semi-Automatic  Turret  Lathe.     Turret  is  Automatically  Revolved 

at  End  of  Each  Stroke 
Courtesy  of  Bullard  Machine  Tool  Company,  Bridgeport,  Connecticut 

end  of  the  return  stroke.  It  is  hexagonal  in  form,  and  the  six  faces 
are  not  only  drilled  and  reamed  for  holding  tools,  but  the  faces  are 
accurately  surfaced,  and  are  drilled  and  tapped  so  that  large  tools 
and  special  devices  may  be  bolted  to  them  when  necessary  or  desir- 
able. An  elaborate  and  useful  system  of  adjustable  stops  controls 
and  limits  the  travel  of  individual  turret  tools.  The  cross-slide  is 
designed  more  upon  the  lines  of  an  engine  latjie  carriage,  and  has 
attached  to  it  an  apron  which  carries  the  necessary  gearing  for  feed- 
ing purposes.  The  carriage  carries  tool-posts  for  one  front  and  two 
back  tools.  The  movement  of  the  carriage  on  the  cuts  is  limited  by 
pivoted,  adjustable  stops  for  each  of  the  three  tools.  There  is  a 
system  of  piping  for  the  lubrication  of  the  turret  tools,  and  another 


MACHINE  SHOP  WORK 


237 


for  the  three  carriage  tools.  The  headstock  is  triple-geared  so  as  to 
give  various  gear  as  well  as  belt  speeds  and  a  powerful  drive  for 
heavy  wrork.  These  changes  of  the  gear  speeds  are  made  by  levers, 
without  stopping  the  machine.  The  main  spindle  is  hollow  so  as  to 


take  bars  through  it,  and  the  chucks  are  adapted  to  take  round, 
hexagonal,  or  square  bars.  There  is  a  taper  attachment  at  the  back 
of  the  carriage,  by  means  of  which  tapered  as  well  as  straight  work 
can  be  turned  by  the  carriage  tools. 

A  very  complete  turret  lathe  is  shown  in  Fig.  297,  as  an  example 


238 


MACHINE  SHOP  WORK 


of  class  5.  The  turret  is  mounted  upon  a  carriage  fitted  to  the  V's 
of  the  bed,  and  provided  with  an  apron  carrying  the  feeding  mech- 
anism. The  turret  is  not  set  upon,  a  horizontal  support  and  pivoted 
on  a  vertical  stud,  as  in  the  former  examples,  but  it  is  inclined  toward 
the  back  of  the  machine  for  the  purpose  of  elevating  the  long  turret 
tools  out  of  the  way  of  the  operator.  The  turret  is  hexagonal,  and 
the  faces  drilled  and  reamed  for  holding  cylindrical  shanked  tools, 
and  also  accurately  faced,  drilled,  and  tapped  for  bolting  on  large  and 
heavy  special  tools  and  devices.  The  turret  is  revolved  automati- 
cally, and  the  cutting  movement  is  controlled  and  limited  by  indi- 
vidual adjustable  stops  for  each  turret  tool.  The  lateral  movement 


I)      (3 


Fig.  298.     "Prentice"  High-Speed  Turret  Lathe 
Courtesy  of  Reed-Prentice  Company,  Worcester,  Massachusetts 

of  the  turret  is  produced  by  a  lead  screw  of  very  sharp  pitch,  so  that 
the  return  stroke  is  not  only  automatic  but  rapid.  Upon  a  heavy 
carriage,  designed  upon  the  lines  of  a  heavy  engine  lathe  carriage,  is 
mounted  a  revolving  tool-post  adapted  to  carry  four  tools  for  cutting- 
off ,  forming,  turning,  etc.  A  taper-turning  attachment  is  located  at  the 
rear  of  the  carriage,  whereby  tapered  work  may  be  as  readily  turned 
as  straight  work.  The  lateral  movement  of  the  carriage  is  con- 
trolled and  limited  by  four  adjustable  stops  at  the  left,  thus  provid- 
ing individual  stops  for  the  tool-post  tools.  Stops  are  also  provided 
for  their  transverse  cuts.  A  system  of  piping  is  provided,  whereby 
all  tools  may  be  lubricated  by  oil  or  other  lubricant,  under  pressure 


MACHINE  SHOP  WORK  239 


from  a  rotary  oil-pump.  This  form  of  lathe  is  built  very  substan- 
tially, and  is  intended  for  the  machining  of  large  and  heavy  castings. 
For  this  purpose  the  turret  as  well  as  the  carriage  is  equipped  with 
long  and  heavy  tools,  some  of  which  will  be  illustrated  and  described 
later  on.  The  headstock  of  this  lathe  is  very  large  and  substantially 
built,  and  is  triple-geared  so  as  to  give  it  great  driving  power  for 
heavy  work.  It  is  driven  by  an  electric  motor,  the  rheostat  for 
which  is  seen  at  the  extreme  left  of  the  engraving,  near  the  floor. 
In  Fig.  298  is  shown  an  automatic  turret  lathe  built  by  the  Reed- 
Prentice  Company  of  Worcester,  Massachusetts. 

Fig.  299  shows  what  is  known  as  the  flat  turret  lathe,  so  called 
from  the  design  of  the  turret.    In  this  case  the  tools  are  not  placed 


Fig.  299.     Flat  Turret  Lathe,  with  Special  Tools  Bolted  to  Top  of  Flat  Plate 
Courtesy  of  Jones  and  Lamson,  Springfield,  Vermont 

in  tool  holes  in  the  outside  of  the  turret  nor  bolted  to  the  faces  of  it. 
On  the  contrary,  they  are  bolted  down  to  the  upper  surface  of  a 
horizontal,  circular  plate.  It  is  a  radical  and  most  successful  inno- 
vation in  the  designing  of  a  turret  lathe,  and  requires  tools  and  fixtures 
specially  designed  for  its  use. 

In  other  examples  we  have  what  is  called  the  hollow  hexagonal 
turret,  which,  instead  of  being  made  solid  as  in  Fig.  293  and  numerous 
other  examples,  consists  of  walls  of  sufficient  thickness  to  properly 
support  the  tool-holders  and  the  tools  bolted  to  it. 

Turret=Lathe  Tools.  A  great  variety  of  tools  are  used  in  the 
turret  lathe,  for  an  indefinite  number  of  uses,  as  the  different  forms 
of  pieces  to  be  machined  are  of  a  never-ending  variety  of  shapes  which 


240  MACHINE  SHOP  WORK 

almost  defies  any  attempt  at  analysis  or  classification.  It  is  possible, 
however,  in  a  general  way,  to  separate  these  tools  according  to  the 
work  which  they  are  designed  to  do,  as  follows: 

(1)  FOR  THE  TURRET:    Centering  tools,    drills,  reamers,    coimterbores. 
FOR  THE  CROSS-SLIDE:  Cutting-off  tools  and  plain  forming  tools,  as  for  fin- 
ishing the  end  of  the  bar  after  a  machined  piece  is  cut  off,  cutting  a  groove  in 
the  work  before  it  is  cut  off,  etc. 

(2)  FOR  THE  TURRET:  Plain  box  tools  containing  a  turning  tool  and  a 
back  rest,  both  adjustable  to  different  diameters;  taps  and  threading  dies  and 
holders  for  the  same;  forming  tools  that  may  be  run  on  the  end  of  a  cylindrical 
piece  of  work.     FOR  THE  CROSS-SLIDE  :  In  addition  to  the  cutting-tools,  horizon- 
tally   moving    and    vertically    moving    forming    tools.      (Occasionally     these 
tools  may  be  so  made  as  to  move  in  an  inclined  direction.) 

(3)  FOR  THE  TURRET:  Box  tools  carrying  several  turning  or  forming 
tools,  or  both,  with  the  necessary  back  rests,  bushings,  etc.     FOR  THE  CROSS- 


Fig.  300.     Split  Collet  §      Fig.  301.     Plain  Drill  Holder 

SLIDE:  Facing  tools;  multiple  tool-holders,  carrying,  turning,  cutting-off,  and 
forming  tools,  and  special  tool-posts. 

(4)  This  class  includes  a  large  number  of  special  tools  and  fixtures  for  use 
in  both  the  turret  and  cross-slide,  by  which  a  great  variety  of  work  of  all  sizes 
and  forms  is  successfully  machined. 

Tools  for  the  Turret.  Drills,  reamers,  boring  bars,  counter- 
bores,  etc.,  may  have  shanks  formed  upon  them,  or  may  fit  in  collets 
fitted  to  the  tool-holes  in  the  turret,  or  in  plain  drill-holders.  A  split 
collet  is  shown  in  Fig.  300;  and  a  plain  drill-holder,  in  Fig.  301. 

Taps  and  dies  may  be  held  in  the  releasing  holder  shown  in 
Fig.  302.  The  shell  A  is  fitted  to  the  tool-hole  in  the  turret,  through 
which  the  shank  of  the  holder  B  passes  and  is  permitted  to  revolve 
freely,  except  when  the  two  are  locked  together  by  the  pins  CC  when 
pressure  is  applied  against  the  face  of  the  die-holder,  or  by  the  pin 
D  when  pressure  is  exerted  in  the  opposite  direction.  In  the  medium 
position,  both  pins  are  inoperative.  This  permits  right-  and  left- 
hand  dies  to  be  used,  the  machine  being  reversed  at  the  proper 
moment. 


MACHINE  SHOP  WORK 


241 


Fig.  302.     Releasing  Holder 


Fig.  303  shows  a 
simple  form  of  box  tool, 
in  which  A  is  the  shank 
entering  the  tool-hole  in 
the  turret;  BB  are  the 
cutting  tools,  adjusted 
by  the  screws  bb;  and  CC 
are  the  jaws  of  the  back- 
rest device  adjusted  to 
the  diameter  of  the 
turned  portion  of  the 
work  by  the  screws  cc. 
Of  the  two  tools,  the 
leading  one  is  for  rough- 
ing, and  the  other  for 
finishing. 

In  the  box  tool 
shown  in  Fig.  304,  the 
two  tools  BB  are  adjust- 
able with  relation  to  each 
other;  hence  two  shoul- 
ders may  be  turned  upon 
a  piece  of  work  simulta- 
neously, at  a  required^ 
distance  apart.  One  box 
tool  may  make  the 
roughing  cuts,  and  in  the 
next  tool-hole  may  be  a 
similar  box  tool  with  its 
tools  set  to  make  the 
finishing  cuts.  The  back- 
rest jaw  C  is  also  adjust- 
able, so  as  to  keep  it  di- 
rectly back  of  the  lead- 
ing tool.  If  the  box  tool  Fig304  DoubleBoxTool 
is  so  constructed  as  to 

have  the  tools  BB  at  a,  considerable  distance  apart,  two  back-rest 
jaws  may  be  necessary,  being  set  in  the  slots  shown. 


242 


MACHINE  SHOP  WORK 


Fig.  305.     Simple  Tool  Clamp 


Fig.  305  shows   a 
simple   form    of   tool 
clamp  in  which  a  variety 
of  tools  having  square  or 
rectangular  shanks,  such 
as   inside   boring   tools, 
may   be   clamped,  thus 
enabling  the  operator  to 
use  ordinary  lathe  tools  for  many 
simple  jobs. 

Fig.  306  shows  a  turret- 
holder  for  a  tool-post  B,  adapted 
to  tools  similar  in  form  and  pur- 
pose to  those  of  Fig.  304,  but 
with  greater  rigidity,  as  the 
shank  A  is  secured  in  the  tool- 
hole,  and  the  cap  screws  CC  hold 
it  rigidly  to  the  face  of  the  turret. 

.    3Q7      ShoWS     a     Well- 


Fig.  306.     Turret  Holder  for  Tool-Post 

designed  box-tool  device,  providing  for  two  tools  and  four  back-rest 
jaws,  all  adjustable  in  any  direction  that  may  be  necessary.     At 


Fig.  307.     Box  Tool  Holder  for  Two  Toola  and  Four  Back-Rest  Jaws 

A  is  the  shank  to  be  entered  in  the  tool  hole  in  the  turret;  BB 
are  the  two  tools;  and  CCCC  are  the  four  back-rest  jaws. 


MACHINE  SHOP  WORK  243 

The  large  tools  that  are  bolted  to  the  faces  of  the  turret  will  be 
shown  in  the  engravings  illustrating  turret-lathe  operations. 

In  Fig.  308  is  shown  a  well-designed  form  of  cross-slide,  carrying 
two  tools  very  rigidly  secured  and  capable  of  adjustment  in  all 
directions  horizontally;  the  tools  may  also  be  inclined.  The  base  A 
supports  the  two  tool-blocks  carrying  the  tools  BB.  The  base  A 
may  be  moved  transversely  across  the  lathe-bed  by  means  of  the 
hand-wheel  C,  which  is  a  very  steady  and  well-controlled  movement 
suitable  for  broad-faced  forming  tools  or  for  facing  tools;  for  narrow 


Fig.  308.     Cross-Slide  Carrying  Two  Tools 

or  cutting-off  tools,  recourse  is  had  to  the  rack-and-pinion  device 
operated  much  more  rapidly  by  the  lever  D. 

The  tools  held  in  the  tool-holders  (commonly  called  box  tools), 
in  tool-posts,  or  in  the  various  styles  of  tool-holders  for  the  cross- 
slide,  and  in  many  of  the  special  tool-holders  of  fixtures,  are  usually 
short  pieces  cut  from  a  square  or  rectangular  bar  of  tool  steel  of 
suitable  dimensions  for  the  work  and  the  holding  fixture.  They  are 
roughly  shaped  at  the  cutting  point,  hardened,  and  then  ground  to 
the  form  desired.  In  using  what  is  commonly  known  as  high-speed 
steel  for  these  tools,  short  pieces  are  broken  from  the  bar;  and  the 
proper  forms  for  the  cutting  point  or  edge  are  obtained  by  grinding, 


244  MACHINE  SHOP  WORK 

no  forging  operation  being  necessary.  While  the  forms  usually 
used  in  lathe  tools  are  also  used  in  tfris  class  of  cutting  tools,  there 
are  many  others,  the  particular  form  of  work  to  be  done  determining 
their  shape. 

Turret=Lathe  Operations.  The  particular  sphere  of  the  turret 
lathe,  and  the  use  of  the  various  tools  and  tool-holding  devices,  can 
be  best  explained  by  illustrating  and  describing  some  of  the  more 
important  operations  in  the  machining  of  castings  of  the  usual 
forms. 

Some  of  the  practical  observations  applicable  to  the  handling 
of  the  work  and  the  tools  are  given,  and  their  importance  should  be 
fully  realized  by  the  novice  in  attempting  turret-lathe  work. 

Great  care  should  be  used  to  have  all  tools,  tool-holders,  attach- 
ments, fixtures,  etc.,  securely  clamped  in  place,  so  that  there  will 
be  no  danger  of  their  working  loose,  and  vibration  will  be  eliminated 
as  far  as  possible. 

The  tools  should  be  ground  to  the  correct  shape,  and  the  finish- 
ing tools  should  be  carefully  stoned  with  a  fine-grained  oil-stone  so 
that  their  cutting  edges  will  be  smooth  and  kee.n.  They  will  then 
do  much  smoother  work,  and  the  cutting  edges  will  last  much  longer. 

Generally  there  must  be  a  roughing  and  a  finishing  cut,  the  same 
as  in  an  ordinary  lathe.  In  the  turret  lathe  the  two  cuts  are  made 
by  different  tools,  so  as  to  avoid  constant  changes  of  adjustment. 

Stop-gages  should  be  carefully  set  so  that  correct  dimensions 
may  be  produced  when  the  turret  slide  or  cross-slide,  as  the  case  may 
be,  is  run  firmly  against  the  stop,  but  so  that  there  is  no  straining  or 
forcing  of  it.  Unless  care  is  used  in  this  respect,  correct  dimensions 
cannot  be  maintained. 

Proper  speeds  must  be  used,  according  to  the  material  to  be 
machined  and  the  diameter  of  the  work.  The  same  speeds  will  be 
used  as  for  engine  lathes.  When  tapping  or  threading  dies  are  used, 
the  speed,  on  the  cut,  must  be  very  materially  reduced. 

In  chucking  comparatively  thin  cylindrical  work,  it  should  be 
held  by  the  outside,  as  there  is  much  less  danger  of  breaking  it  than 
if  it  is  held  by  the  inside. 

In  machining  heavy-rimmed  balance  wheels,  they  are  frequently 
held  by  the  inside  of  the  rim  so  as  to  leave  the  outside  and  face  clear 
for  the  tools. 


MACHINE  SHOP  WORK 


245 


Pulleys  and  similar  light  wheels  are  frequently  held  by  the 
arms,  which  rest  against  suitable  supports  so  as  to  avoid  distortion 
and  to  leave  the  rims  and  hub  free  for  machining  operations. 

In  boring  operations,  particularly  deep  holes,  the  tool  should  be 
made  with  a  long  guiding  end  or  pilot,  which  may  enter  a  bushing  in 
the  main  spindle  of  the  machine  before  the  tool  commences  to  cut. 
This  will  reduce  vibration  and  chatter,  insure  a  true  hole,  and  prolong 
the  life  of  the  tool. 

When  the  piece  of  work  is  comparatively  long — that  is,  projects 
to  a  considerable  distance  from  the  chuck — the  outer  end  should  be 


Fig.  309.     Turret  Lathe  Arranged  to  Machine  Webbed  Balance  Wheel 

run  in  a  center  rest  similar  to  that  on  an  engine  lathe,  to  hold  it  true 
and  rigid,  and  to  insure  true  and  accurate  work. 

Fig.  309  is  a  plan  of  the  chucking  arrangement;  the  turret  and 
its  tools;  and  the  cross-slide  tool-block  of  a  turret  lathe  arranged  to 
machine  a  webbed  balance-wheel.  It  is  to  be  finished  all  over,  and 
must  therefore  require  two  operations. 

First  Operation.  The  wheel  is  chucked  as  shown  at  A  on  the 
inside  of  the  rim,  by  the  chuck-jaws  B<  This  leaves  the  outside  of 


246 


MACHINE  SHOP  WORK 


the  rim  clear  for  the  turning  tools.  The  cored  hole  is  first  rough- 
bored  with  the  cutter  N  in  the  end  of  a  boring  bar  M,  which  is  held 
in  a  steady  rest  or  drill-support  D.  The  hole  having  been  rough- 
bored,  the  boring  bar  M  is  withdrawn,  and  the  steady  rest  D  thrown 
back  out  of  the  way.  The  turret  is  rotated  so  as  to  bring  the  bor- 
ing bar  Mi  into  position.  The  forward  end  of  this  bar  is  supported 
by  a  bushing  H  in  the  main  spindle.  The  two  cutters  NI  and  Nz 
are  for  roughing  out  the  hole  preparatory  to  using  the  taper  reamer 
<2  on  another  face  of  the  turret.  While  boring  with  the  bar  MI,  the 
scale  is  broken  on  the  web  and  hub  by  the  tool-post  tools  shown  at 


TTire*  Jawed  Chu 


Fig.  310.     Arrangement  for  Machining  Spur-Gear  Blank 


J  and  K.  The  scale  on  the  periphery  is  broken  by  the  tool  J.  The 
turret  is  revolved  so  as  to  bring  the  taper  reamer  Q  into  position, 
and  the  end  of  its  bar  enters  a  bushing  in  the  main  spindle.  A  taper 
bushing  C  is  inserted  in  the  taper  hole  for  receiving  the  supporting 
arbor  or  pilot  T  in  the  facing  head,  as  shown  at  the  top  of  the  engrav- 
ing. The  balance-wheel  is  rough-faced,  and  the  outer  surface  of  the 
rim  turned  with  the  cutters  E,  G,  H,  and  F  in  the  facing  head.  This 
brings  the  piece  approximately  to  size.  For  finishing  these  surfaces, 
the  cutters  GI,  EI,  Hlf  and  Fi,  in  the  finishing  head  are  used,  this 
head  being  supported  in  the  taper  bushing  d.  The  finishing  cuts 
are  very  light. 

Second  Operation.     These  cuts  being  completed,  the  balance- 
wheel  is  removed  from  the  chuck,  reversed,  and  again  placed  in  the 


MACHINE  SHOP  WORK  247 

chuck,  which  has  in  the  meantime  been  equipped  with  slip  jaws  of 
soft  metal,  bored  out  so  as  to  exactly  fit  the  curvature  of  the  wheel. 
The  piece  is  still  further  supported  by  a  tapered  arbor  projecting 
from  the  hole  in  the  main  spindle  and  accurately  fitting  the  taper- 
reamed  hole.  The  turret  is  equipped  with  tools  similar  in  form  and 
purpose  to  those  described.  The  scale  is  broken  by  tools  in  the 
rotating  tool-posts,  as  in  the  first  operation.  The  first  set  of  tools 
rough  off  the  face  of  the  rim  and  hub,  and  face  the  web.  The  second 
set  finishes  these  surfaces  completely,  and  the  operation  is  completed. 
The  operations  for  machining  a  spur-gear  blank  are  well  shown 
in  Fig.  310.  In  this  case  a  flat  turret  is  used  on  the  machine  shown  in 


Fig.  311.     Turret  Lathe  Arranged  to  Machine  Outside  of  Cone  Pulley 

Fig.  299.  At  A  is  shown  a  section  of  the  finished  piece  of  work, 
giving  the  actual  dimensions.  The  casting  is  chucked  by  the  hub, 
as  shown  at  B.  At  each  of  the  other  five  faces  the  piece  of  work  is 
represented  as  mounted,  with  the  tool  arranged  in  proper  relation 
to  it  to  make  the  required  cut.  The  rough  boring  having  been  com- 
pleted, the  turret  is  revolved  to  the  next  face,  and  the  hook  tool  C 
faces  the  back  of  the  hub.  Upon  the  next  turn  of  the  turret,  the 
boring  tool  D  makes  a  finishing  cut  in  the  bore,  bringing  it  to  an 
exact  diameter.  Another  turn  of  the  turret,  and  the  bar  E,  with  its 
inside  facing  cutter,  faces  the  rear  side  of  the  rim,  while  a  facing  cutter 
e  faces  the  front  of  the  hub.  It  will  be  noticed  that  the  tool-holder  H 
travels  along  the  slide  J,  thus  providing  for  the  necessary  feed  for 
both  the  tools  E  and  e.  The  next  movement  of  the  turret  brings  into 


248  MACHINE  SHOP  WORK 

action  the  finishing  tools  F  and/,  which  finish  the  rear  face  of  the  rim 
and  the  front  face  of  the  hub,  operating  in  a  similar  manner  to  the 
tools  E  and  e.  A  final  turn  of  the  turret  brings  the  round-nosed  turn- 
ing tool  G  into  position,  and  turns  the  outside  diameter  of  the  gear 
blank,  completing  the  operation.  Upon  this  machine,  provided  with 
the  tools  shown  and  operated  as  described,  an  iron  casting  of  the 
dimensions  given  can  be  completely  machined  by  an  expert  operator 
in  from  eight  to  ten  minutes.  The  same  work  done  upon  an  engine 
lathe  would  require  four  or  five  times  as  long. 

A  much  more  complicated  series  of  operations  is  presented  in 
Figs.  311  and  312.     In  Fig.  312  is  shown  the  first  of  the  series  of 


Fig.  312.     Arrangement  for  Machining  Inside  of  Cone  Pulley 


operations,  comprising  the  machining  of  the  inside  of  the  cone.  In 
Fig.  311  the  series  of  operations  necessary  to  finish  the  outside  are 
shown.  Referring  to  Fig.  312,  it  will  be  seen  that  the  cone-pulley 
casting  A  is  supported  upon  the  second  step  from  the  small  end  by 
the  cylindrical  base  B.  Within  this  the  three  jaws  of  the  chuck  grasp 
the  smallest  step  of  the  cone,  holding  it  very  rigidly  and  securely  in 
place.  The  boring  bar  C  carries  the  cutters  for  rough-boring  the 
cored  hole.  Its  inner  end  is  supported  by  a  bushing  in  the  main 
spindle,  as  shown  in  Fig.  309.  The  next  turn  of  the  turret  brings  the 
boring  bar  D  into  action,  which  finishes  the  hole  to  the  proper  diam- 


MACHINE  SHOP  WORK  249 

eter.  The  next  tool  E  faces  the  edge  of  the  rim  on  the  largest  step  of 
the  cone.  The  face  F  of  the  turret  carries  no  tool.  Tool  G  is  a  very 
important,  compound  tool  whose  work  is  to  finish  the  inside  of  the 
larger  three  steps,  and  also  to  face  the  annular  surfaces  between  the 
steps.  It  consists  of  a  massive  casting,  bolted  to  the  turret  face  and 
divided  into  three  double-ended  arms,  each  of  these  ends  carrying  a 
tool  of  proper  form  for  the  inside  turning  and  facing,  making  six 
tools  in  all.  Through  the  center  of  this  tool-holder  is  an  arbor  or 
steadying  bar  g,  which  passes  through  the  bushing  in  the  main 
spindle  and  holds  the  tool-carrier  steady  and  in  its  proper  central 
position.  The  tool  H  serves  to  finish  the  inside  of  the  largest  step, 
for  a  short  distance  from  the  face,  to  the  accurate  diameter  for 
fitting  the  flange  that  supports  this  end  and  furnishes  a  hub  through 
which  its  shaft  or  spindle  passes. 

The  second  series  of  operations  is  shown  in  Fig.  311.  These 
operations  consist  of  machining  the  outside  of  the  cone-pulley  casting 
A,  that  portion  of  the  inside  of  the  larger  end  finished  by  the  tool  H 
in  the  first  series  of  operations  fitting  over  a  circular  disc  B,  through 
slots  in  which  the  chuck  jaws  are  forced  outwardly  against  the  cone 
casting.  In  fixing  the  casting  in  position,  an  arbor  C  projects  from 
the  bored  hole,  and  is  entered  in  a  reamed  hole  of  the  same  diameter 
in  the  centering  fixture  D  attached  to  the  turret,  whereby  the  outer 
end  of  the  cone-pulley  casting  is  quickly  and  accurately  centered. 
This  fixture  also  serves  as  an  excellent  support  for  the  outer  end  of 
the  cone  during  the  process  of  turning  and  facing  the  outer  surfaces. 
The  special  revolving  tool-block  E  carries  on  one  side  five  tools  for 
turning  the  outside  of  the  cone  steps,  as  shown  in  the  illustrations, 
and,  on  the  opposite  side,  five  facing  tools  for  facing  the  annular 
surfaces  between  the  steps.  In  the  operation  of  turning  the  outer 
surfaces,  it  is  necessary  to  crown  them — that  is,  to  make  the  center  of 
each  step  of  slightly  larger  diameter  than  at  the  two  edges,  as  in 
ordinary  pulleys.  To  accomplish  this,  the  taper  attachment  F  is 
brought  into  use,  being  set  to  give  the  larger  diameter  on  the  side 
toward  the  chuck  and  turning  half  the  width  of  the  outer  surface;  the 
setting  is  then  reversed  for  turning  the  other  half.  As  all  five  sur- 
faces are  turned  or  faced  simultaneously,  the  operation  is  very  rapid 
when  compared  with  the  work  of  an  engine  lathe.  The  inside  of  the 
small  end  of  the  cone  is  finished  with  the  tools  G  and  H  in  the  usual 


250  MACHINE  SHOP  WORK 

manner.     In  all  turret  operations,  the  lateral  travel  of  the  turret  is 
controlled  and  limited  by  the  revolving  multiple-stop  device  at  J. 

There  are  many  devices  and  adjunct  fixtures  in  use  upon  the 
turret  lathe;  and  their  number,  as  well  as  the  ingenuity  of  their  design 
and  the  extent  of  their  usefulness,  is  constantly  increasing.  So 
numerous  are  they  that  no  attempt  is  here  made  to  show  and  describe 
them.  The  same,  in  a  lesser  degree,  may  be  said  of  the  turret-lathe 
tools.  At  the  same  time,  there  is  a  very  large  range  of  work  con- 
stantly done  on  turret  lathes  with  the  most  ordinary  equipment.  It 
was  formerly  assumed  that  the  turret  lathe  could  be  used  with  econ- 
omy only  when  at  least  a  hundred  pieces  were  to  be  machined.  It  is 
ordinary  practice  at  the  present  day  to  use  the  turret  lathe  when  as 
few  as  a  dozen  pieces  (and  sometimes  less)  are  required.  As  the 
value  of  the  turret  lathe  and  its  efficiency  come  to  be  better  under- 
stood, its  usefulness  is  better  realized  and  appreciated. 

AUTOMATIC  SCREW  MACHINES 

The  automatic  screw  machine,  in  its  design  and  method  of 
operation,  is  a  highly  developed  type  of  turret  lathe,  its  cutting  tools 
being  carried  in  some  form  of  turret.  By  the  term  turret,  as  used  in 
this  connection,  is  understood  a  revolving,  multiple  tool-holder, 
whether  rotating  on  a  vertical  or  on  a  horizontal  axis;  and  whether 
consisting  of  a  single  casting  having  the  necessary  tool-carrying 
appendages,  or  of  a  cylindrical  form  carrying  a  series  of  sliding,  tool- 
carrying  spindles.  The  principles  upon  which  it  is  designed  and 
constructed,  and  upon  which  it  operates,  are  the  same. 

The  automatic  screw  machine,  as  originally  designed,  was 
intended  principally  for  making  small  screws  and  studs;  hence  it 
was  called  a  screw  machine.  The  flexibility  of  its  plan,  and  its 
adaptability  to  a  large  range  of  operations,  encouraged  its  develop- 
ment along  other  lines  of  work.  Normally  it  was  adapted  to  making 
screws,  studs,  and  similar  work  from  a  bar,  which  was  passed  through 
its  hollow  spindle  from  the  back  of  the  machine,  and  was  pressed 
forward  against  a  stop  carried  in  one  of  the  tool-holes  in  the  turret 
whenever  the  chuck  was  opened  sufficiently  to  release  the  bar  of  stock. 
The  device  which  fed  the  bar  through  was  operated  by  a  weight,  and 
was  called  a  wire  feed,  originally  from  the  fact  that  screws  were  made 
from  pieces  of  straightened  wire.  The  same  device,  built  of  sufficient 


MACHINE  SHOP  WORK  251 

weight  and  strength,  is  capable  of  feeding  quite  large  bars  of  stock 
through  a  machine  of  many  times  the  capacity  thought  possible 
in  the  early  years  of  the  development  of  this  machine.  This 
wire  feed  device  operated  automatically,  it  only  being  required  to 
introduce  a  new  bar  when  that  in  the  machine  was  used  up. 

The  predominant  feature  in  the  design  of  the  automatic  screw 
machine,  after  the  use  of  the  turret,  is  the  employment  of  drum  cams, 
upon  which  are  fixed  a  series  of  removable  cam  members  suitable 
.to  the  piece  of  work  to  be  made,  and  by  which  the  automatic  move- 
ments of  the  different  operative  parts  of  the  machine  are  produced. 
It  is  because  of  the  action  of  these  cams  that  the  machine  is  classed 
as  automatic. 

By  automatic,  we  mean  a  machine  in  which  all  of  the  movements 
are  mechanically  made,  including  the  bringing  of  a  new  length  of 
work  through  the  chuck,  upon  which  the  various  operations  are  made 
in  succession  so  that  the  operator  has  only  to  keep  the  cutting  tools 
sharp  and  to  put  in  another  bar  of  stock  when  one  has  been  entirely 
used  up.  By  semi-automatic,  we  mean  a  machine  in  which  the  rough 
piece  of  wrork  is  placed  in  the  chuck  by  the  operator,  and  on  which  all 
the  various  operations — such  as  drilling,  boring,  reaming,  forming, 
facing,  etc. — are  mechanically  performed,  as  well  as  the  rotation  of 
the  turret.  Thus  the  machine  operating  on  bar  work  can  readily  be 
made  automatic  in  a  strict  definition  of  the  term;  while  if  the  pieces 
are  small  and  separate  castings,  drop  forgings,  and  the  like,  they  must 
be  placed  in  the  chuck  by  the  operator,  and  the  chuck  closed,  before 
the  automatic  work  of  the  machine  commences. 

There  are  built,  however,  machines  of  this  class,  in  which  the 
castings  or  drop  forgings  are  placed  in  a  sort  of  magazine  or  hopper, 
whence  they  pass  to  the  chuck,  in  which  they  are  gripped  ready  for 
the  subsequent  machining  operations,  this  work  being  entirely  auto- 
matic and  the  only  attention  required  from  the  operator  being  that 
of  keeping  the  magazine  full  of  pieces  and  the  tools  sharp  and  properly 
adjusted. 

Types  of  Automatic  Screw  Machines.  Manufacturing  Auto- 
matic Chucking  and  Turning  Machine.  Fig.  313  shows  a  Potter  and 
Johnson  machine,  called  by  them  a  manufacturing  automatic 
chucking  and  turning  machine.  It  is  a  good  example  of  a  semi- 
automatic machine  which  has  nearly  all  the  features  of  the  typical 


252 


MACHINE  SHOP  WORK 


automatic  screw  machine,  and  at  least  one  feature  that  is  not  adapt- 
able to  a  machine  making  the  pieces  of  work  from  a  bar  run  through 
the  hollow  spindle  and  carrying  cutters  by  which  the  back  of  a  piece 
of  work  held  in  the  chuck  is  automatically  faced.  This  is  accom- 
plished through  the  lever  C,  rod  D,  and  cam  E. 

The  headstock  is  triple-geared  so  as  to  provide  for  ample  power 
for  heavy  work,  this  gearing  being  changed  to  the  desired  speeds  by 
a  simple  lever  mechanism.  The  turret  is  mounted  in  the  same  man- 
ner as  in  a  turret  lathe,  upon  a  laterally  moving  slide.  This,  however, 
is  actuated  by  suitable  connections  to  the  drum  cam  A,  the  cam 


Fig.  313.     Automatic  Chucking  and  Turning  Machine 
Courtesy  of  Potter  and  Johnston  Machine  Company,  Pawtucket,  Rhode  Island 

tracks  of  which  are  composed  of  removable  plates  BB  fitting  the 
surface  and  attached  by  screws.  The  turret  has  five  faces;  conse- 
quently there  are  five  sets  of  these  plates,  which  may  be  so  shaped 
and  arranged  as  to  give  any  length  of  stroke  desired.  Usually  a  full 
stroke  is  given  to  the  turret  slide,  the  act  of  cutting  being  confined 
to  the  latter  part  of  the  stroke.  The  cross-slide  is  equipped  with 
two  tool-posts  FF;  and  the  tools  can  be  arranged  to  work  at  the  same 
time  that  the  turret  tools  are  cutting — or  separately,  as  the  nature 
of  the  work  may  require.  The  cross-slide  may  also  be  provided  with 
tool-blocks  for  carrying  blades  or  forming  tools  for  special  work.  It 
is  operated  through  a  rack-and-pinion  device  from  a  cam  G,  and  the 
triangular  actuating  blocks  upon  this  cam  can  be  adjusted  in  any 
required  positions  around  the  circle  that  may  be  necessary  to  produce 


MACHINE  SHOP  WORK  253 

the  required  movements.  The  cams  A,  G,  and  E  are  fixed  to  the 
same  shaft,  which  makes  but  one  revolution  during  the  cycle  of 
movements  necessary  to  complete  one  piece  of  work.  This  feature 
is  the  same  in  all  the  different  types  of  this  class  of  machines. 

While  the  machine  shown  was  designed  for  handling  separate 
pieces  of  work,  as  castings,  drop  forgings,  etc.,  the  removal  of  the 
back  facing  bar,  and  the  substitution  of  a  wire  or  rod  feed  with  an 
automatically  operated  chuck,  would  convert  it  into  a  machine 
adapted  to  machine  pieces  automatically  from  the  bar. 

The  latest  type  of  Potter  and  Johnston  chucking  and  turning 
machine  is  shown  in  Fig.  314. 

Cleveland  Automatic  Machine.  Fig.  315  shows  a  Cleveland 
automatic  machine,  of  which  several  variations  of  the  same  style 


Fig.  314.     Latest  Type  of  Automatic  Chucking  and  Turning  Machine 
Courtesy  of  Potter  and  Johnston  Machine  Company,  Pawtucket,  Rhode  Island 

are  built.  The  main  spindle  A  is  driven  from  the  system  of  pulleys 
B,  the  belt  being  controlled  by  the  automatically  operated  shifter  C. 
At  D  is  shown  the  device  for  opening  and  closing  by  hand  the  chuck 
in  the  head  E  of  the  main  spindle  A  when  setting  the  machine. 
The  mechanism  by  which  the  bar  of  stock  is  forced  forward  through 
the  chuck,  is  at  F. 

The  turret  mechanism  is  at  G,  and  consists  of  a  cylindrical  device 
with  its  axis  in  a  horizontal  position  and  journaled  in  the  housings  at 
//  //,  sliding  in  the  left-hand  housing  in  making  the  cut.  This  form 
of  turret  is  exceedingly  rigid.  The  tool-holes  are  bored  in  the  end  of 


1 


MACHINE  SHOP  WORK 


255 


the  cylindrical  portion  g,  and  the  tools  secured  by  set  screws,  as 
shown.    The  turret  is  moved  forward  and  back  by  a  mechanism  oper- 


ated by  the  shaft  N;  and  is  revolved  on  the  back  stroke  by  suitable 
helical  cams,  a  portion  of  which  is  shown  at  K.     In  setting  the 


256 


MACHINE  SHOP  WORK 


machine,  the  turret  is  operated  by  the  crank  M,  upon  whose  shaft  is 
a  worm  engaging  the  worm  wheel  J. 

The  cross-slide  L  is  arranged  for  two  tool-posts,  and  is  operated 
by  a  suitable  mechanism  in  the  rear.  It  is  adapted  for  carrying  form- 
ing tools  as  well  as  the  usual  cutting-off  tools. 

There  are  a  number  of  interesting  and  valuable  attachments 
furnished  with  these  machines,  among  which  is  one  for  slotting  screw- 
heads,  and  for  slabbing  or  milling  at  a  time,  two  sides  of  square  or 
hexagonal  heads  by  a  straddle  mill.  There  is  also  a  third  spindle 


Fig.  317.     Universal  Multiple-Spindle  Automatic  Screw  Machine 

speed  attachment,  in  which  the  center  pulley  B,  usually  an  idler,  is 
utilized  as  a  driver;  and  by  the  addition  of  a  set  of  differential  gears, 
the  spindle  speed  is  reduced  in  a  ratio  of  three  to  one,  giving  a  slow 
speed  for  threading  large  work.  By  this  means  the  spindle  speed 
can  be  as  rapid  as  is  possible  for  the  use  of  high-speed  steel  tools,  and 
still  have  a  slow  speed  available  for  large  tapping  or  threading. 

In  case  solid  dies  are  used  and  the  threading  done  with  the  belt 
on  the  pulley  B  (now  a  driver),  the  belt  is  thrown  to  one  of  the  other 
pulleys,  and  the  fast  reverse  speed  used  to  run  the  die  off  the  work. 
A  magazine  attachment  is  also  made  for  automatically  feeding  cast- 
ings or  drop  forgings  down  to  the  chuck,  so  as  to  dispense  with  the 


MACHINE  SHOP  WORK  257 

services  of  the  operator  on  this  class  of  work,  except  to  see  that  the 
magazine  is  kept  supplied  with  work. 

In  Fig.  316  is  shown  the  latest  type  of  Cleveland  "automatic". 

Universal  Multiple-Spindle  Automatic  Screw  Machine.  This 
machine,  Fig.  317,  is  of  a  type  distinctively  different  from  either  of 
the  previous  examples.  The  operative  parts  are  operated  mostly 
by  the  usual  drum  cams,  three  of  which,  A,  B,  and  (7,  are  used. 
The  peculiarity  of  the  design  of  this  machine  is  that  the  work  is 
carried  in  five  revolving  spindles  at  Z),  while  axially  opposite  them 
are  five  tools.  The  revolving  spindles  carry  five  bars  of  stock,  upon 
all  of  which  work  is  being  done  simultaneously.  The  results  secured 
by  this  arrangement  are  that  the  work  necessary  for  completely 
finishing  a  piece  is  no  longer  than  that  required  for  performing  the 
longest  single  operation,  regardless  of  the  number  of  operations 
required  on  the  piece. 

The  machine  is  driven  by  a  single  belt  upon  the  pulley  F,  the 
power  being  transmitted  by  spur  gearing  to  the  center  shaft  G,  which 
runs  through  the  spindle  head  //,  at  the  left  of  which  it  is  connected 
by  spur  gears  with  the  five  spindles  at  D.  There  are  three  cross- 
slides  J,  K,  and  L,  the  tools  of  which  act  at  the  same  time  as  the  box 
tools  or  other  tools  usually  carried  in  a  turret.  The  cam  shaft  carry- 
ing the  cams  A,  B,  and  C  is  driven  by  a  belt  from  the  pulley  M  to 
the  two  pulleys  N,  which,  by  means  of  differential  gearing,  give  two 
speeds  to  the  shaft;  on  the  latter  is  a  worm  engaging  the  worm  wheel 
P,  thus  providing  for  a  rapid  speed  for  indexing,  and  a  quick  advance 
and  return  of  the  tools.  The  belt  is  shifted  automatically  to  the 
inner  pulley,  which  drives  the  shaft  slower  for  the  feeding  of  the 
tools  on  the  cut.  The  squared  end  of  the  cross-shaft  provides  for 
a  crank  which  may  be  used  to  rotate  the  mechanism  when  setting  the 
machine. 

The  design  of  the  machine  is  very  ingenious,  and  its  output  on 
small  work  should  be  very  large  in  consequence  of  having  five  or  more 
tools  continuously  employed  during  the  time  that  in  the  usual  type 
of  machine  there  is  one  (or,  at  most,  two)  in  active  operation. 

Brown  and  Sharpe  Automatic  Screw  Machine.  This  machine, 
shown  in  Fig.  318,  is  of  a  type  quite  distinct  from  any  of  those  above 
described.  It  will  be  noticed  that  the  machine  is  very  compact  when 
compared  with  some  of  tne  others  previously  illustrated.  This 


258 


MACHINE  SHOP  WORK 


being  the  case,  it  is  necessary  to  show  sectional  and  other  views, 
in  order  properly  to  explain  the  mechanism  so  that  it  may  be 

understood. 

Fig.  319  is  a  front 
elevation  showing  a  sec- 
tion through  the  spindle, 
spindle  boxes,  pulleys, 
etc.  The  main  spindle 
runs  in  phosphor-bronze 
boxes.  The  front  bearing 
is  adjustable,  and  is  ad- 
justed by  nuts  1  and  2. 
The  thrust  is  taken  by  a 
hardened  steel  washer  5, 
and  adjusted  by  the  nut 
4-  Friction  clutch  pulleys 
10,  running  on  ball  bear- 
ings, drive  the  spindle. 

Fig.  320  is  a  rear  ele- 
vation of  the  machine, 
and  is  introduced  to  illus- 
trate more  completely 
its  construction. 

The  friction  clutches 
are  conical;  the  clutch  bodies  1 1,  Fig.  319,  are  forced  into  the  pulleys 
by  sliding  the  sleeve  over  the  levers  12,  which  have  for  one  fulcrum 


Fig.  318.    Brown  and  Sharpe  Automatic  Screw  Machine, 

No.  00  Size 

Courtesy  of  Brown  and  Sharpe  Manufacturing  Company, 
Providence,  Rhode  Island 


Fig.  319.     Front  Elevation  of  Brown  and  Sharpe  Automatic  Screw  Machine,  Showing 
Section  through  Spindle 

the  screw  in  the  clutch  body,  and  for  the  other  a  notch  in  the 
spindle.    To  adjust  for  wear,  loosen  clamp  screw  15,  and  turn  nut  13. 


MACHINE  SHOP  WORK 


259 


The  clutch  sleeves  are  set  central,  to  give  an  equal  pressure  on 
both  pulleys,  by  means  of  the  screws  27.  In  making  this  adjustment, 
there  is  a  slight  play  allowed  in  the  clutch  fork  to  avoid  friction, 
except  at  the  point  of  reversal. 

The  spindle  is  reversed  to  run  backward  by  the  spring  plunger 
42,  which,  when  released,  instantly  engages  the  clutch  with  the 
pulley  nearest  the  chuck.  To  run  forward,  the  clutch  is  reversed  by 
the  cam  31,  to  engage  the  other  pulley.  This  cam  is  operated  by 
the  clutch  32,  and  at  the  end  of  the  revolution  is  drawn  out  by  the 
lever  23.  At  the  time  of  reversing  the  spindle  to  run  forward,  the 


Fig.  320.     Rear  Elevation  of  Brown  and  Sharpe  Automatic  Screw  Machine 

action  of  the  cam  compresses  the  plunger  spring  ready  for  the  next 
reversal;  the  plunger  is  held  in  place  by  the  wide  part  of  the  lever  22. 
The  levers  22  and  23  are  lifted  to  reverse  the  spindle  at  the  proper 
time,  by  adjustable  dogs  on  the  carrier,  shown  below  them  in  Fig.  319. 
If  the  work  is  to  be  threaded,  this  carrier  shaft  is  connected  by  the 
positive  clutch  24  to  the  cut-off  cam  shaft  18.  When  changing 
cut-off  cams,  the  clutch  is  disengaged  and  can  remain  in  this  posi- 
tion, for  work  not  threaded.  Should  it  be  desired  to  both  thread 
and  tap  work,  or  to  cut  two  threads  on  the  same  piece,  two  or  more 
sets  of  dogs  can  be  used  on  the  carrier. 

The  spring  collet  that  holds  the  stock  has  no  end  movement, 
thus  providing  for  the  accurate  feeding  of  the  stock  regardless  of 
slight  variations  in  size.  It  is  closed  by  means  of  the  sleeve  6, 


260  MACHINE  SHOP  WORK 

Fig.  319,  which  is  tapered  inside  and  slides  over  the  collet.  This 
sleeve  is  operated  by  the  tube  extending  through  the  spindle  to  the 
chuck-levers  7,  which  in  turn  are  operated  by  the  sleeve  8  through 
the  lever  and  cam  25.  The  chuck  mechanism  is  operated  and  the 
chuck  fed  by  the  cam  25,  which  is  driven  through  spur  gears  83,  by 
the  positive  clutch  89  on  the  driving  shaft.  By  depressing  the  lever 
underneath  the  clutch,  shown  in  Fig.  320,  the  clutch  is  engaged  and 
makes  one  revolution;  it  is  then  disengaged  by  the  pin  in  the  lever 
acting  upon  the  cam  surface  of  the  clutch,  and  returns  to  its  original 
position. 

To  adjust  the  chuck,  the  nut  17  is  loosened,  and  the  nut  16 
turned  until  the  holding  capacity  of  the  chuck  is  properly  regulated; 
then  the  nut  17  is  tightened,  and  both  nuts  are  locked  by  means  of 
the  spanner  wrenches  provided. 

The  main  feed-shaft  14  is  driven  by  the  pulley  shown  at  the  head 
of  the  machine.  This  pulley  is  engaged  by  a  positive  clutch  oper- 
ated by  the  starting  lever  21,  Fig.  319.  Thus  the  feed  is  always 
under  complete  control.  A  hand  wheel  provided  with  a  handle  is 
used  for  operating  the  mechanism  when  setting  the  machine. 

The  stock  is  fed  in  the  usual  manner  by  a  feed-tube,  the  outer 
end  of  which  is  connected  by  a  latch  to  the  slide  28.  This  slide  has 
a  slot  in  which  is  a  sliding  block  connecting  it  to  the  lever  29,  which 
in  turn  is  operated  by  the  cam  25.  The  sliding  block  is  adjusted  by 
a  screw  and  crank,  as  shown  in  Fig.  320,  and,  as  the  lever  29  always 
moves  a  fixed  distance,  the  length  of  feed  is  regulated  by  varying  the 
position  of  the  block.  A  graduated  scale  is  mounted  on  the  slide, 
and  indicates  the  length  of  feed. 

The  feeding  fingers  are  changed  by  lifting  the  latch  at  the  rear 
end  of  the  tube,  and  withdrawing  the  feed-tube.  These  fingers  are 
threaded  left-hand. 

When  it  is  desired  to  feed  more  stock  than  the  usual  capacity  of 
the  machine,  two  or  more  dogs  can  be  used  on  the  left  side  of  carrier 
19,  Fig.  319,  and  the  feeding  mechanism  operated  several  times. 

The  turret  1+5  is  mounted  vertically  on  the  side  of  the  turret 
slide,  Fig.  319.  It  has  a  long  taper  shank  that  forms  the  bearing  in 
the  turret  slide,  and  is  rotated  by  a  hardened  roll  in  the  disc  35, 
Fig.  320,  which  engages  the  radial  grooves  in  the  disc  34  on  the  rear 
end  of  the  turret  shank.  The  revolutions  of  the  turret  are  thus 


MACHINE  SHOP  WORK  261 

made  very  rapidly  and  with  no  noticeable  shock.  It  is  locked  in 
position  by  a  hardened  taper  pin  which  is  withdrawn  by  a  cam. 

The  turret  slide  receives  its  forward  motion  for  the  cutting  tools 
through  a  bell-crank  lever  operated  by  a  cam  on  the  shaft  40,  Fig.  320, 
which  is  driven  through  spur  gears  by  the  shaft  and  worm  gear  J^l . 

The  quick  return  and  advance  of  the  turret  slide,  and  the  revolv- 
ing of  the  turret,  are  controlled  independently  of  the  turret-slide 
feed-cam,  by  a  crank,  while  the  roll  on  the  bell-crank  lever  is  passing 
from  the  highest  point  of  the  turret-slide  feed-cam  to  the  point  of 
starting  the  next  cut.  The  crank  is  operated  by  gears  at  the  rear  of 
the  machine,  driven  by  the  positive  clutch  38,  Fig.  320,  on  the  driv- 
ing shaft,  writh  lever  and  other  parts  for  making  one  revolution,  as 
described  in  connection  with  the  feeding  mechanism.  As  the  crank 
revolves,  it  allows  a  spring  to  return  the  turret  slide  without  the 
rack.  The  turret  is  then  revolved  as  described;  and  when  the  crank 
comes  to  rest  after  making  one  complete  revolution,  the  machine  is 
ready  for  the  next  operation. 

The  cross-slides  are  operated  by  the  cut-off  cam  shaft  18, 
Fig.  319',  which  is  driven  through  bevel  gears  by  the  worm-wheel 
shaft  41,  Fig.  320. 

The  front  slide  has  a  direct  lever  or  segment  of  a  gear;  the  back 
slide  has,  in  addition,  an  intermediate  lever  or  segment  to  reverse  the 
motion,  thus  bringing  the  cams  for  operating  both  slides  into  a 
convenient  position.  The  form  of  that  part  of  the  cam  controlling 
the  quick  movement  of  the  slides  is  the  same  for  both.  The  seg- 
ments mesh  into  racks  that  extend  beyond  the  slides.  The  outer 
end  of  these  racks  is  threaded  and  provided  with  nuts  for  adjusting 
the  cuts  of  the  tools.  Stop-screws  are  also  provided  to  insure 
accuracy  in  forming. 

The  cross-slide  tools  have  circular  shanks,  and  are  held  in  place 
by  screws.  Eccentric  nuts  are  provided  on  screws  that  allow  the 
tools  to  be  easily  and  quickly  adjusted  to  the  proper  height.  These 
tools  are  sharpened  on  the  face  without  changing  the  outline,  the 
same  as  formed  milling  cutters. 

The  tools  are  lubricated  by  a  geared  oil-pump  of  ample  capacity, 
provided  with  suitable  piping.  The  pump  is  not  stopped  with  the 
disengaging  of  the  feed-clutch,  thus  insuring  a  large,  steady  stream 
of  oil  as  soon  as  the  tools  begin  to  cut. 


262 


MACHINE  SHOP  WORK 


In  Fig.  321  is  shown  a  No.  2  Brown  and  Sharpe  automatic 
screw  machine. 

Hollow  Mills.  For  turning  the  bodies  of  small  screws,  the 
shoulders  on  studs,  and  many  similar  operations,  hollow  mills  are 
used.  A  simple  form  of  one  of  these  is  shown  in  Fig.  322,  which  has 
three  cutting  edges.  An  improved  form  is  shown  in  Fig.  323,  con- 
sisting of  a  collar  through  which  pass  three  set  screws,  their  points 


Fig.  321.     Number  2  Automatic  Screw  Machine 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company,  Providence,  Rhode  Island 

bearing  upon  each  of  the  cutting  sections,  by  which  means  they  can 
be  adjusted  when  so  worn  that  work  comes  too  large.  A  better  form 
of  the  hollow  mill  is  shown  in  Fig.  324,  which  is  constructed  with  three 
adjustable  blades,  whereby  the  tool  may  be  set  for  a  Considerable 
variation  in  diameter. 

Setting=Up  the  Machine.    A  variety  of  types  of  automatic  screw 
machines  have  been  shown  and  described,  in  order  that  the  reader 


MACHINE  SHOP  WORK 


263 


Fig.  322.     Hollow  Mill  with  Three 
Cutting  Edges 


may  familiarize  himself  with  those  built  by  different  manufacturers, 
and  so  be  able  to  handle  whatever  kind  he  may  be  required  to  set-up 
for  the  job  in  hand.  The  great  variety  of  work  which  the  turret 
lathe  and  the  screw  machine  are 
called  upon  to  perform,  renders  it 
impossible  to  describe  all  the  oper- 
ations necessary  for  such  work; 
but  a  few  general  directions  may 
be  given  that  will  nearly  always 
apply: 

When  making  work  from  the  bar,  it  is  first  necessary  to  select 
and  place  in  the  machine  the  proper  chuck,  and  to  arrange  at  the  rear 
end  of  the  main  spindle  for  the  support  of  that  end  of  the  bar.  If  a 
rod  feed  is  used,  that  is  next  attended 
to.  A  stop  is  now  fixed  in  one  of  the 
tool-holes  in  the  turret,  against  which 
the  end  of  the  bar  is  forced  by  the 
automatic  rod-feed.  This  stop  is  set 
so  that  the  bar  may  be  forced  out  of 
the  chuck  only  far  enough  to  make 
the  required  piece,  and  to  furnish 
space  for  the  cutting-off  tool  of  the 
tool-slide  to  wTork.  The  box  tools  should  next  be  set,  and  the  cut- 
ters adjusted  to  the  diameter.  The  adjustable  stops  for  the  travel 
of  the  turret  for  each  cut  will  now  be  adjusted,  the  machine  started, 
and  each  tool  brought  into  action 
and  its  adjustment  corrected.  Sup- 
posing that  two  box  tools  are  used, 
the  stop  will  be  in  tool-hole  No.  1, 
and  the  box  tools  in  Nos.  2  and  3. 
If  the  job  requires  very  accurate  di- 
ameters, a  roughing  and  a  finishing 
box  tool  will  be  needed  for  that  por- 
tion requiring  the  delicate  work. 
This  will  be  No.  4.  If  the  smaller 
diameter  is  to  be  threaded,  the  die  will  be  set  in  No.  5.  If  this 
is  a  solid  die,  the  belt  shifter  must  be  set,  by  the  proper  location 
of  the  dogs  on  the  shifter  cam  to  produce  the  reversed  motion  for 


Fig.  323.     Improved  Hollow  Mill 


Fig.  324.     Hollow  Mill  with  Three 
Adjustable  Blades 


264  MACHINE  SHOP  WORK 

backing  off  the  die,  and  then  for  the  forward  motion  of  the  next  cut. 
A  pointing  tool  may  be  set  in  No.  6  for  finishing  the  end  of  the  piece 
after  the  thread  has  been  cut.  The  cutting-off  tool  is  now  adjusted. 
In  some  cases  the  back  tool  of  the  cross-slide  is  made  a  forming  tool 
for  finishing  the  end  of  the  piece  that  is  to  be  cut  from  the  bar,  or 
for  rounding  or  chamfering  it;  after  which  the  cutting-off  tool 
advances  and  severs  it  from  the  bar.  These  operations  having  been 
provided  for,  the  chuck-operating  cam  is  adjusted  to  open  the  chuck 
at  this  point,  permitting  the  rod-feed  device  to  force  the  bar  through 
and  against  the  stop  in  tool-hole  No.  1,  after  which  it  should  immedi- 
ately close  on  the  bar,  and  the  cycle  of  movements  be  repeated. 
The  drum  cam  for  producing  the  lateral  movement  of  the  turret  will 
not  usually  need  to  be  changed.  The  mechanism  for  revolving  the 
turret  will  ordinarily  be  left  without  readjustment  in  setting-up  the 
machine  for.a  new  job. 

If  separate  pieces,  as  castings  or  drop  forgings,  are  to  be 
machined,  the  first  operation  is  usually  boring  the  hole;  then  reaming 
it.  If  a  considerable  degree  of  accuracy  is  required  in  the  diameter 
of  the  hole,  there  will  be  a  roughing  and  a  sizing  cut  before  using  the 
reamer.  The  succeeding  cuts  will  depend  so  much  upon  the  shape 
and  the  necessary  working  surfaces  of  the  piece,  that  no  general 
sequence  of  operations  can  be  given. 

There  is  probably  no  machine  in  the  modern  manufacturing 
plant  that  requires  greater  ingenuity  and  fertility  of  resources  than 
the  selection  and  setting-up  of  the  automatic  machine  so  as  to  realize 
the  greatest  measure  of  economy  and  efficiency. 


MACHINE  SHOP  WORK 

PART  V 


MODERN  MANUFACTURING 

Machine  Building  vs.  Machine  Manufacturing.  While  machine 
work  in  general,  and  the  use  of  machine  tools  in  particular  are 
much  the  same  in  all  shops,  the  methods  employed  in  machine 
building  and  in  machine  manufacturing  are  essentially  different. 

Construction  Methods.  In  machine  building  only  a  small  num- 
ber of  machines  are  built  in  a  single  lot  and  it  is  seldom  that  they 
are  worked  upon  in  any  consecutive  order.  For  example,  while 
several  machines  of  the  same  kind  may  be  under  construction,  they 
may  stand  in  all  stages  of  construction  from  that  of  those  nearing 
completion  or  even  completed  to  some  upon  which  construction  has 
just  begun.  In  some  shops,  this  is  so  much  the  fact  that  machines 
are  constructed  only  after  the  order  for  them  has  been  placed.  When 
manufacturing  machines,  however,  the  process  is  a  very  different 
one.  Here  the  work  is  done  in  lots  of  considerable  size  and  each 
operation  on  each  piece  is  consecutively  performed. 

Types  of  Workmen.  The  workmen  in  a  shop  producing 
machines  by  manufacturing  methods  are  differently  placed  than  they 
are  in  shops  building  machines  in  small  lots,  perhaps  a  machine  at 
a  time  only.  In  the  latter  case  the  workmen  may,  during  the  same 
day,  perform  lathe  work,  milling,  drilling,  bench,  and  floor  work; 
while  in  a  shop  which  manufactures  machines  in  considerable  lots, 
the  workmen  usually  works  on  one  machine  during  the  term  of 
employment.  This  has  led  to  the  development  of  workmen  who 
term  themselves  lathe  hands,  planer  hands,  etc.,  each  workman 
specializing  in  the  handling  of  a  single  machine  tool  and  seeking 
employment  as  a  specialized  machinist.  In  certain  shops,  notably 
those  building  automobiles,  this  specializing  process  has  proceeded 
to  such  an  extent  that  the  workman  performs  but  a  single  operation 
on  a  machine.  For  example,  he  may  be  employed  on  a  lathe  to  square 
up  the  end  of  crank  shafts,  which  come  to  him  in  sufficient  quantities 


266  MACHINE  SHOP  WORK 

to  keep  him  continuously  employed  during  his  working  day.  If 
the  shop  is  run  on  a  twenty-four  hour,  three-shift  basis,  he  may  in 
this  case  be  one  only,  of  three  workmen,  each  of  whom  does  the  same 
operation  on  the  same  single  purpose  machine. 

PRODUCTION  METHODS 

Single  Purpose  Machines.  If  the  reader  has  carefully  followed 
the  above,  he  will  realize  somewhat  the  extent  to  which  modern 
organization  of  workmen  has  proceeded.  Another  development 
has  been  the  construction  of  single  purpose  machines.  For  example, 
Fig.  350,  page  294,  shows  a  machine  constructed  for  the  single 
purpose  of  drilling  the  clearance  holes  on  solid  threading  dies.  On 
this  machine  a  single  operation  only  can  be  performed,  but  by  the 
use  of  four  spindles  and  five  work-holding  chucks,  a  die  is  com- 
pletely finished  at  one  stroke  of  the  table.  Single  purpose  machine 
tools  of  any  sort  can  now  be  bought  in  the  open  market,  as,  for  exam- 
ple, single  purpose  lathes,  grinding  machines,  etc. 

In  other  cases,  instead  of  purchasing  single  purpose  machines, 
the  regular  types  have  been  changed  by  the  use  made  of  special 
attachments,  tools,  jigs,  and  fixtures,  to  perform  either  a  single 
operation  only,  or  at  least  a  slight  range  of  operation. 

Specialized  Cutting  Steels.  Modern  investigations  have  led 
to  the  adoption  of  specialized  cutting  methods  and  cutting  tools 
in  up-to-date  manufacturing.  At  the  very  center  of  these  shop 
efficiency  methods  stands  the  newer  types  of  cutting  steels.  These 
have  so  revolutionized  metal  cutting  operations  that  production 
has  been  in  many  cases  more  than  doubled. 

Cutting  Lubrication.  By  means  of  properly  designed  machines 
and  pumps,  and  by  experiment  in  the  uses  and  nature  of  numerous 
oils  and  mixtures,  it  is  now  common  practice  in  some  lines  of  cutting 
to  practically  submerge  the  cutting  operation  writh  some  one  of  the 
several  cutting  lubricants. 

Cutting  Speeds.  These  have  been  increased  from  the  older 
series  of  possible  cutting  speeds  to  an  extent  which  has  led  one 
enthusiast  to  predict  that  the  time  was  not  far  distant  when  steel 
and  iron  would  be  cut  as  rapidly  as  wood. 

Cutting  Feeds.  The  great  increase  in  the  weights  and  con- 
sequent rigidity  and  massiveness  of  the  present-day  machine  tools, 


MACHINE  SHOP  WORK  267 

as  well  as  the  modern  work-holding  devices,  has  made  possible  an 
increased  feeding  of  the  cutting  tool  little  realized  by  the  older 
machinist. 

Automatics.  Under  this  head  may  be  classed  those  machines 
which  produce  the  work  in  a  more  or  less  completely  finished  state 
with  the  least  attention.  While  no  machine  is  so  constructed  that 
it  can  be  classed  as  fully  automatic,  there  are  many  on  the  market 
which  are  so  complete  in  their  action  that  a  single  attendant  will 
care  for  and  keep  in  operation  as  many  as  a  dozen  machines. 

Automatic  Control.  Much  advance  has  been  made  in  recent 
years  in  devising  means  of  controlling  the  operation  of  machines 
from  a  central  point.  Electrical,  hydraulic,  and  pneumatic  devices 
have  been  and  are  being  introduced  which  have  for  their  objective 
the  possibility,  when  once  the  machine  has  been  adjusted,  of  con- 
trolling its  operations  by  the  movement  of  a  lever  or  the  pressing 
of  a  button.  Such  a  control  is  already  in  certain  use  upon  large 
planers,  boring  mills,  etc. 

Cold  Worked  Metals.  It  has  been  found  that  certain  machine 
parts,  such  as  screws,  shafts,  pulleys,  etc.,  can  be  formed  into  their 
proper  contours  by  pressing,  rolling,  or  squeezing  processes,  in  a 
manner  which  admits  of  a  lesser  first  cost,  than  that  of  cutting  them 
from  the  solid  in  a  lathe,  milling  machine,  or  other  machine  tool. 
As  this  work  is  performed  without  a  previous  heating  of  the  stock, 
it  is  classed  as  "cold  working". 

Die  Casting  Machine  Parts.  This  process  consists  in  casting, 
in  suitable  closed  dies  under  pressure",  a  previously  melted  alloy. 
Parts  of  small  and  delicate  machinery  as  well  as  instruments 
are  often  produced  in  this  manner  so  accurate  in  dimension  and 
perfect  in  finish  that  they  are  assembled  without  added  machine 
work. 

Special  Molding  Processes.  Machine  manufacturing  is  in  many 
cases  confined  to  producing  a  machine,  many  of  whose  parts  are 
made  of  iron  castings  in  which  exact  accuracy  of  fitting  is  not  neces- 
sary. The  ordinary  loom  and  certain  lines  of  agricultural  machinery 
are  notable  examples  of  such  machines.  By  construction  of  special 
molding  processes,  notably  that  of  machine  molding,  it  is  possible 
to  produce  many  machine  parts  sufficiently  accurate  to  render  them 
directly  usable  after  having  been  cleaned  and  common  snags  removed. 


268  MACHINE  SHOP  WORK 

Special  Die  Forgings.  While  the  ordinary  forged  piece  is 
seldom  suited  for  use  in  accurate  machine  construction  without 
previous  machining,  several  firms  are  now  producing  special  die 
forged  machine  parts  of  an  accuracy  in  dimensions  and  perfection 
of  finish  that  leaves  little  to  be  desired. 

Heat  Treatment.  Under  this  head  comes  the  modern  method 
of  giving  to  many  machine  parts  such  as  spindles,  shafts,  gears, 
cones,  clutches,  and  many  others,  a  special  heating  and  cooling 
treatment.  The  production  performances  of  our  modern  machines 
are  in  many  cases  made  possible  only  because  the  constructor  has 
learned  that  certain  steel  parts  when  heated  and  cooled  in  a  pre- 
determined scientific  manner  are  given  an  added  strength  to 
resist  wear  or  breakage. 

Ball  Bearings.  The  use  in  machines  of  specialized  ball  bear- 
ings has  gained  rapidly  in  recent  years.  While  in  the  case  of  machine 
tools  their  use  has  been  more  largely  confined  to  such  machines 
as  drillers,  their  certain  use  is  everywhere  self-evident. 

Bearing  Alloys.  Where  accuracy  of  bearing  and  closeness  of 
fitting  is  especially  desirable,  the  older  type  of  plain  bearing  is 
believed  by  many  machine  construction  engineers  to  be  the  better. 
To  ensure  the  proper  wearing  qualities  under  the  varying  conditions 
of  service,  it  has  become  desirable  that  the  several  bearing  alloys 
be  carefully  studied  and  their  characteristics  tabulated. 

Bearing  Lubrication.  Correct  proportions  of  bearing  surface 
to  the  load,  a  suitable  bearing  alloy,  and  assured  bearing  lubrication 
are  sought.  In  studying  bearing  lubrication,  all  these  must  be 
considered. 

Drives.  Belt  Drives.  The  belt  manufacturer  has  helped  to 
solve  this  problem  by  producing  belting  suited  to  the  machine  con- 
structor's needs.  Most  conditions  of  temperature,  humidity,  and 
pliability  have  been  met  by  the  belt-maker.  Many  experiments 
have  been  made  and  published  by  engineers  to  show  what  a  given 
belt  may  be  expected  to  do  under  varying  conditions  of  heat,  cold, 
and  dampness. 

Geared  Drives.  Machines  designed  for  heavy  roughing  cuts 
are  often  provided  with  a  complete  geared  driving  mechanism  in 
which  all  the  speed  changes  are  made  through  trains  of  gearing  and 
engaging  clutches. 


MACHINE  SHOP  WORK  269 

Motor  Drives.  Instead  of  driving  by  means  of  trains  of  belting 
there  is  an  increasing  tendency  toward  the  use  of  direct  driving. 
This  is  usually  done  by  direct  connection  of  an  electric  motor  to 
the  driving  mechanisms.  In  shops  where  the  machines  are  fitted 
with  individual  motors,  it  may  be  so  complete  that  no  belting  is 
to  be  observed. 

Jigs  and  Fixtures.  Where  strict  interchangeability  of  parts  is 
essential,  special  work-holding  and  tool-locating  devices  are  indis- 
pensable if  a  low  manufacturing  cost  is  to  be  attained.  These  are 
known  as  jigs  and  fixtures. 

Time  Study.  The  nearer  to  a  minimum  cost  a  machine  can 
be  constructed  while  maintaining  a  proper  commercial  standard, 
the  greater  are  the  chances  that  the  business  will  be  successful. 
It  is,  therefore,  among  other  things,  extremely  important  that  the 
lowest  possible  labor  cost  shall  be  ascertained.  In  modern  efficiency 
work,  an  exhaustive  time  study  is  made  of  each  operation  performed 
in  the  shop  until  definite  time  figures  are  obtained  and  recorded  in 
the  manager's  office. 

Motion  Study.  This  term  is  used  to  designate  that  particular 
line  of  investigation  which  has  for  its  objective  the  elimination 
of  all  unnecessary  movements  in  performing  a  given  piece  of  work. 
Investigation  has  shown  that  an  untrained  workman  when  per- 
forming even  the  simplest  of  operations  may,  and  usually  does,  make 
many  entirely  useless  movements  to  get  his  results. 

Overheads.  Under  this  name  are  classed  all  those  expenses 
of  manufacture  which  cannot  be  as  directly  charged  to  production 
as  can  labor  cost  and  the  cost  of  materials.  They  include  such 
items  as  heat,  power,  light,  insurance,  depreciation,  taxes,  office 
help,  executives,  beside  others,  and  are  known  as  the  shop  burden. 

Selling  Costs.  The  cost  of  selling  the  manufactured  machines 
may  or  may  not  be  charged  to  their  cost  under  the  head  of  "over- 
heads". In  any  case  it  must  be  at  least  approximated  if  not  exactly 
known  and,  of  course,  charged  along  with  the  previous  items  to  the 
production  costs. 

PRODUCTION  MACHINES 

The  brief  review  of  modern  machine  methods  given  in  the 
preceding  pages  indicate  the  trend  of  the  developments  being  made 
by  the  progressive  construction  engineers.  The  modern  machine 


270 


MACHINE  SHOP  WORK 


constructor  makes  use  of  the  work  of  scientists  whenever  it  touches 
his  line  of  production,  and  in  fact  is  ever  reaching  out  and  searching 
the  world  for  new  production  ideas.  In  the  following  section  will 
be  briefly  described  and  illustrated  a  few  of  the  more  modern  special 
or  specialized  machine  tools  used  in  machine  manufacturing. 

GRINDING  MACHINES 

Range   of   Usefulness.     While   in   many   shops   the   grinding 
machine  is  used  only  as  a  finishing  tool  on  parts  which  require  a 


Fig.  325.     Example  of  Steady  Rests  as  Employed  by  Norton  Grinding  Company 
Courtesy  of  Norton  Grinding  Company,  Worcester,  Massachusetts 

special  surface,  or  in  which  greater  accuracy  is  required  than  is 
readily  reached  by  the  other  machine  tools,  in  modern  work  shops 


MACHINE  SHOP  WORK  271 

it  is  one  of  the  large  production  factors.  The  work  which  comes 
to  the  grinding  machine  has  usually  been  rough  turned  to  an  approx- 
imate diameter,  but  in  many  instances  it  has  been  found  that  the 
grinding  machine  will  completely  finish  the  piece  of  work  from  the 
rough  stock  at  a  lesser  labor  cost,  doing  its  own  roughing  and  finish- 
ing. This  is  especially  true  when  long  slender  shafts  are  produced. 
Automobile  crank  shafts,  for  example,  are  commonly  ground  from 
the  rough. 

Cylindrical  Grinding.  Producing  cylinders  of  revolution  is 
one  of  the  more  common  uses  to  which  grinding  machines  are  put. 
This  is  usually  accomplished  by  traversing  a  rotating  abrasive  wheel 


Tig.  326.     Traverse  Markings  on  Piece  of  Ground  Work 

in  contact  with  the  rotating  piece  of  work,  as  in  Fig.  325.  In  this 
operation  the  rotating  wheel  can  be  made  to  feed  along  the  length 
of  the  work  by  giving  the  work  table  a  traversing  motion  along 
the  bed  of  the  machine.  Some  of  the  things  to  be  noted  in  this 
machine  are:  (a)  Its  large  wheel  spindle  with  generous  journals 
making  it  possible  to  use  abrasive  wheels  large  in  diameter  with 
broad  faces;  (b)  the  abrasive  wheel  bearing  stand  giving  large 
spindle  bearings  and  great  rigidity;  (c)  a  heavy  traversing  table 
with  large  bearing  area  upon  the  bed;  (d)  the  work-supporting 
rests;  and  (e)  the  general  massiveness  of  construction. 

Wheel  Speed.  The  peripheral  or  surface  speed  of  the  abrasive 
wheel  is  usually  held  pretty  closely  to  5500  linear  feet  per  minute. 
While  in  some  cases  a  wheel  speed  of  6500  feet  per  minute  or  as 


272 


MACHINE  SHOP  WORK 


TABLE  XI 

Revolutions  per  Minute  for  Various  Sizes  of  Grinding  Wheels  to 
Give  Peripheral  Speed  in  Feet  per  Minute 


DIAMETER 
OF  WHEEL 
IN  INCHES 

4003 

4500 

£000 

5500 

cooo 

0500 

1 

15,279 

17,200 

19,099 

21,000 

22,918 

24,850 

2 

7,639 

8,590 

9,549 

10,500 

11,459 

12,420 

3 

5,093 

5,725 

6,366 

7,000 

7,639 

8,270 

4 

3,820 

4,295 

4,775 

5,250 

5,730 

6,205 

5 

3,056 

3,440 

3,820 

4,200 

4,584 

4,970 

6 

2,546 

2,865 

3,183 

3,500 

3,820 

4,140 

7 

2,183 

2,455 

2,728 

3,000 

3,274 

3,550 

8 

1,910 

2,150 

2,387 

2,635 

2,865 

3,100 

10 

1,528 

1,720 

1,910 

2,100 

2,292 

2,485 

12 

1,273 

1,543 

1,592 

1,750 

1,910 

2,070 

14 

1,091 

1,228 

1,364 

1,500 

1,637 

1,773 

16 

955 

1,075 

1,194 

1,314 

1,432 

1,552 

18 

849 

957 

1,061 

1,167 

1,273 

1,380 

20 

764 

860 

955 

1,050 

1,146 

1,241 

22 

694 

782 

868 

952 

1,042 

1,128 

24 

637 

716 

796 

876 

955 

1,035 

26 

586 

661 

733 

809 

879 

955 

28 

546 

614 

683 

749 

819 

887 

30 

509 

573 

637 

700 

764 

827 

32 

477 

537 

596 

657 

716 

776 

34 

449 

506 

561 

618 

674 

730 

36 

424 

477 

531 

534 

637 

689 

38- 

402 

453 

503 

553 

603 

653 

40 

382 

430 

478 

525 

573 

621 

42 

364 

409 

455 

500 

546 

591 

44 

347 

391 

434 

477 

521 

564 

46 

332 

374 

415 

456 

498 

539 

48 

318 

358 

397 

438 

477 

517 

50 

306 

344 

383 

420 

459 

497 

52 

294 

331 

369 

404 

441 

487 

54 

283 

318 

354 

389 

425 

459 

56 

273 

307 

341 

366 

410 

443 

58 

264 

296 

330 

354 

396 

428 

60 

255 

277 

319 

350 

383 

414 

low  as  4500  feet  per  minute  may  give  good  results,  wheel  speed  does 
not  in  general  practice  vary  much  from  the  5500  feet  given.  Table 
XI  gives  wheel  speeds  used  in  good  practice. 

Wheel  Traverse.  This  is  taken  as  the  distance  the  abrasive 
wheel  travels  axially  during  a  complete  revolution  of  the  work. 
While  experts  differ  as  to  what  proportion  of  the  face  of  the  wheel 
this  should  be,  it  would  appear  that  where  operating  conditions 
will  stand  it,  a  traverse  of  above  one-half  the  wheel  face  width  per 
work  revolution  is  desirable  when  rough  grinding  work.  Fig.  326 
shows  the  traverse  markings  upon  a  piece  of  ground  work. 


MACHINE  SHOP  WORK  273 

Grinding  Allowances.  When  in  grinding  practice  the  work 
has  been  previously  rough  turned,  it  is  customary  to  leave  an  amount 
of  stock  to  be  removed  in  the  grinding  machine  dependent  upon 
the  size  and  character  of  the  work  and  upon  the  roughing  out  method 
employed. 

Table  XII  gives  allowances  left  for  grinding  as  worked  out  by 
the  Landis  Tool  Company.  If  the  roughing  out  is  done,  using  an 
exceptionally  coarse  feed,  as  shown  in  Fig.  327,  the  tabulated  allow- 


Fig.  327.     Roughing-Out  for  Grinding  Showing  Heavy  Cut 

ances  will  need  to  be  exceeded.  It  is  well  to  note  here  that  tab- 
ulated grinding  details -in  machine  construction  are  useful  chiefly 
as  a  starting  basis. 

Abrasive  Wheels.  Large  enterprises  are  devoted  to  the  pro- 
duction of  artificial  abrasives.  Increased  knowledge  in  the  man- 
ufacture of  the  wheels  themselves  and  an  added  knowledge  in  wheel 
selection  has  materially  changed  the  abrasive  wheel  industry  from 
that  of  previous  years.  The  greater  portion  of  modern  machine 
grinding  is  now  done  with  the  manufactured  abrasives.  These 
are  in  most  part  very  efficient  in  cutting  qualities  and  are  sold  under 
a  variety  of  trade  names  such  as.  alundum,  aloxite,  carborundum, 


274 


MACHINE  SHOP  WORK 


TABLE  XII 
Allowances  for  Grinding* 


DIAM- 
ETER 
(in.) 

LENGTH 

(in.) 

3 

6 

9 

12 

15 

18 

24            30 

36 

42 

48 

ALLOWANCE 
(in.) 

| 

0.010 

0.010 

0,010 

0.010 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

£ 

0.010 

0.010 

0.010 

0.010 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

4t 

1 

0.010 

0.010 

0.010 

0.015 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

H 

0.010 

0.010 

0.015 

0.015 

0.015 

0.015 

•0.015 

0.020 

0.020 

0.020 

0.020 

4 

0.010 

0.015 

0.015 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

0.020 

2 

0.015 

0.015 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

0.020 

0.025 

2? 

0.015 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

0.020 

0.025 

0.025 

2| 

0.015 

0.015 

0.015 

0.020 

0.020 

0.020 

0.020 

0.020 

0.025 

0.025 

0.025 

3 

0.015 

0.015 

0.020 

0.020 

0.020 

0.02Q 

0.020 

0.025 

0.025 

0.025 

0.025 

3| 

0.015 

0.020 

0.020 

0.020 

0.020 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

4 

0.020 

0.020 

0.020 

0.020 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 

4£ 

0.020 

0.020 

0.020 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

5 

0.020 

0.020 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

6 

0.020 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

7 

0.020 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

0.030 

8 

0.025 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

9 

0.025 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

10 

0.025 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

11 

0.025 

0.025 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

12 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

0.030 

crystolon,  and  several  others.  Abrasive  wheels  can  be  had  also  in 
a  variety  of  degrees  of"  hardness,  coarseness,  and  varying  bonds,  as 
is  seen  by  consulting  Tables  XIII  and  XIV.  Degrees  of  hardness, 
coarseness,  and  bonding  condition  make  up  what  is  known  as  the 
"grain"  and  the  "grade"  of  the  abrasive  wheel. 

Grinding  Methods.  Skilled  Operators.  The  larger  manufac- 
turers of  grinding  machines  have  representatives  trained  to  the 
highest  skill  in  operating  their  line  of  machines.  A  purchaser  of 
their  machines  can  have  one  of  these  highly  skilled  operators  demon- 
strate the  maximum  efficiency  possibilities  of  the  particular  machine. 

Grinding  Crank  Shafts.  As  a  sample  of  high  speed  grinding 
production  the  finishing  of  automobile  crank  shafts  may  be  taken. 
Fig.  328  shows  the  methods  employed. 

Flat  Face  Grinding.  While  the  work  illustrated  in  Fig.  325  is 
done  by  axially  traversing  a  wheel  having  a  face  width  of  about 
two  inches,  an  increasing  amount  of  work  is  being  done,  using  the 
wheel  as  a  broad  cutting  tool  and  feeding  the  wheel  directly  into  the 

*  From  Landis  Tool  Company,  Waynesboro,  Pennsylvania. 


MACHINE  SHOP  WORK 


275 


work  until  the  desired  diameter  is  obtained.  By  this  method  there 
is  no  axial  traversing  of  the  wheel  while  in  its  cut.  Cup  wheels 
having  a  width  of  face  as  great  as  nine  inches  have  been  used  on 
such  machines  as  shown  in  Fig.  329.  By  means  of  suitable  face 


forming  attachments,  the  face  of  the  wheel  can  be  surfaced  to  a 
variety  of  contours.  It  will  therefore  be  seen  that  the  new  method 
of  grinding  can  be  employed  not  only  for  straight  cylindrical  sur- 
faces, but  for  work  having  an  irregular  contour.  Fig.  330  shows 


276  MACHINE  SHOP  WORK 

TABLE  XIII 
Norton  Grade  List 

The  following  grade  list  is  used  to  designate  the  degree  of  hard- 
ness of  vitrified  and  silicate  wheels,  both  alundum  and  crystolon: 

E Soft 

F 


G 
H 
I. 


.Medium  Soft 


K 
L 
MEDIUM M. ... 

N 
O 
P 
Medium  Hard Q 


MEDIUM 


Hard, 


R 
S 
T 

U 

V 

w 

X 

Extremely  Hard Y 

Z 

The  intermediate  letters  between  those  designated  as  soft,  medium  soft, 
etc.,  indicate  so  many  degrees  harder  or  softer;  e.g.,  L  is  one  grade  or  degree 
softer  than  medium;  0,  two  degrees  harder  than  medium,  but  not  quite  medium 
hard. 

Elastic  wheels  are  graded  as  follows:  1,  1\,  2,  2\,  3,  4,  5,  and  6.  Grade  1 
is  the  softest  and  grade  6,  the  hardest. 

the  correct  form  of  work-supporting  rests.  Figs.  331,  332,  and 
333,  show  how  the  wheel  approaches  the  work  for  straight  and  for 
contour  work. 

Internal  Cylindrical  Grinding.  Machine  grinding  the  internal 
surfaces  of  gas  engine  cylinders  may  be  used  as  a  good  example  of 
this  •  line  of  production  work.  Figs.  334  and  335  show  two  views 
of  such  work.  It  will  be  noted  that  these  views  illustrate  one  of 
several  special  internal  grinding  machines  particularly  designed 
for  this  class  of  work.  The  prominent  feature  in  its  design  is  that 
in  place  of  rotating  the  work  against  the  grinding  wheel,  the  work 
is  rigidly  held  in  a  fixed  position.  By  means  of  a  slow  revolving 


Fig.  329.     Norton  Grinder  with  51-Inch  Face  Wheel  for  Grinding  Ford 
Axles  and  Drive  Shafts 


Fig.  330.     Work  Properly  Supported 

Courtesy  of  Norton  Grinding  Company, 

Worcester,  Massachusetts. 


Figs  331  and  332.     Set-Up  for  Grinding 
Straight  and  Contour  Work  with 

Norton  Grinder 
Courtesy  of  "Machinery",  New  York  City 


278 


MACHINE  SHOP  WORK 

TABLE  XIV 
Selection  of  Grades 


CLASS  OF  WORK 

ALUNDUM                           CRYSTOLON 

Grain 

Grade 

Grain 

Grade 

Aluminum  castings 

Brass  or  bronze  castings  (large) 
Brass  or  bronze  castings  (small) 
Brick,  fire 
Brick,  pressed               % 

Car  wheels,  cast  iron 
Car  wheels,  chilled 
Cast  iron,  cylindrical 
Cast  iren,  surfacing 
Cast  iron  (small)  castings 
Cast  iron  (large)  castings 
Chilled  iron  castings 

Dies,  chilled  iron 
Dies,  steel 
Drop  forgings 

Hammers,  cast  steel 
Hollowware,  inside  grinding 
Hollowware,  thin  edges 

Internal  grinding  of  automobile  cylinders 
(cast  iron) 
Internal  grinding,  hardened  steel 

Knives  (paper)  ,  automatic  grinding 
Knives  (planer),  automatic  grinding 
Knives,  leather  shaving 
Knives,  leather  splitting 
Knives,  molding  bits,  etc. 

Knives  (planing  mill)  ,  hand  grinding 
Knives,  shear  and  shear  blades 
Knives,  shoe 

Lathe  centers 
Lathe  and  planer  tools 

Machine  shop  use,  general 
Malleable  iron  castings  (large) 
Malleable  iron  castings  (small) 
Marble,  finishing 
Marble,  roughing 
Marble,  coping 
Marble,  molding 
Milling    cutters,    automatic    or    semi-auto- 
matic grinding 
Milling  cutters,  hand  grinding 

Nickel  castings 

Pearl  grinding,  roughing 
Pearl  grinding,  finishing 
Plow  bodies  (cast  iron),  surfacing 
Plows  (steel),  jointing 
Plow  points  (chilled  iron),  surfacing 
Plows  (steel),  surfacing 
Porcelain,  roughing 
Pulleys  (e  i)  ,  surfacing  faces  of 

Radiators  (cast  iron),  edges  of 
Razors,  grinding  and  concaving 
Reamers,  taps,  milling    cutters,    etc.,    hand 
grinding 

36  to    46 

3  to  4  Elas. 

20  to    24 

20  to    24 
24  to    36 
16  to    20 
16  to    20 

16  to    24 
16  to    24 
30  to    46 
16  to    30 
20  to    30 
16  to    24 
20  to    30 

20  to    30 

PtoR 

?£8 

Pto  Q 

OtoP 

P  to  Q 
O  to  Q 
J  to  L 
JtoL 
Q  to  S 
Q  to  S 
Q 

O  to  Q 

20 
24  comb. 
20  to    46 
24  to    30 
16  to    20 
20  to    30 

JtoK 
HtoK 
PtoR 
Q  to  R 
PtoU 

"JVo'L" 
PtoR 

P 

36  to    60 
20  to    30 

30 

» 

• 

30 
24 

30  to    60 

8 

I  to  L 

'46  to    60 

36  to    46 
30  to    46 
60 
24  to    30 
f46to    60 
\46to    60 
46  to    60 
30  to    60 
60 

46  to  120 
[20  to    24 
\20to    36 

20  to    36 
14  to    20 
20  to    30 

'J'toM 

JtoK 
JtoK 
N  toO 
1  to  2  Elas. 
3  Elas. 
M 
JtoM 
J  to  M 
M 

J  to  M 
PSil. 
OtoP 

O  to  Q 
PtoU 
PtoR 

'  16  to"  20 
20  to    30 
150  to    F 
16  to    46 
36  to    46 
4 

"Rto'  s" 
QtoS 
M 
M 

O  to  S 
0 

46  to    60 
46  to    60 

20  to    24 

HtoM 
JtoM 

PtoQ 

20  to    24 

30  to    50 
100  to  150 
24 

R 

PtoU 
MtoP 
R 

20  to    24 

Rto  S 

20  to    30 

Q  to  S 

16  to    24 

Q  to  S 

36  to    50 
30  to    36 

24  to    30 

Oto  R 
KtoL 

R  to  S 

46  to  120 
46  to    60 

HtoO 
KtoO 

MACHINE  SHOP  WORK 


279 


TABLE  XIV— (Continued) 
Selection  of  Grades 


CLASS  OF  WORK 

ALUNDUM 

CRYSTOLOV 

Grain 

Grade 

Grain 

Grade 

Reamers,  taps,  milling  cutters,  etc.,  special 
machines 
Rolls  (cast  iron),  wet 
Rolls  (chilled  iron),  finishings 
Rolls  (chilled  iron),  roughing 
Rubber 

Sad  irons,  finishing 
Sad  irons,  roughing 
Saws,  gumming  and  sharpening 
Saws,  cold  cutting-off 
Shovels,  edging 
Spiral  springs,  ends  of 

Steel  (soft),  cylindrical  grinding 

Steel  (soft)  ,  surface  grinding 
Steel  (hardened),  cylindrical  grinding 

Steel  (hardened)  ,  surface  grinding 
Steel,  large  castings 
Steel,  small  castings 
Steel  (manganese),  safe  work 
Steel  (manganese),  frogs  and  switches 
Structural  steel 
Stove  castings 

Twist  drills,  hand  grinding 
Twist  drills,  special  machines 

Wagon  springs,  ends  of 
Wire,  ends  of  steel 
Wrought  iron 
Woodworking  tools 

46  to    60 
24  to    36 
70 

'30  to"  50 

JtoM 
JtoM 
li  to  2  Elas. 

'24  to"  36 
70  to    80 
30  to    46 
30  to    50 

80  to  120 
20  to    30 

"J'toM' 
li  to  2  Elas. 
2  to  3  Elas. 
KtoM 

QtoR 
QtoS 

JtoK 

36  to    50 
60 
24 
16  to    20 

/24  comb. 
\46to    60 
24  to    36 
/24  comb. 
\46to    60 
36  to    46 
12  to    20 
20  to    30 
16  to    46 
14  to    16 
16  to    24 
20  to    36 

46  to    60 
36  to    60 

20  to    30 
36  to    80 
12  to    30 
46  to    60 

M  toN 
0«oQ 

Qto  R 

Lto  N 
Lto  N 
HtoK 
K 
J  to  L 
HtoK 
QtoU 
PtoR 
LtoP 
QtoU 
PtoR 
PtoQ 

M 
KtoM 

PtoR 
QtoR 
P  toU 
KtoM 

.«  

QtoR 

20  to    36 

motion  given  to  the  spindle  carrying  frame,  the  highly  speeded 
rotating  wheel  carrying  spindle  is  itself  carried  about  in  a  circle. 
Provisional  adjustments  can  be  made  to  alter  the  diameter  of  this 
circle  to  meet  changes  in  the  cylinder  dimensions.  When  water 
jacketed  work  is  being  ground,  means  are  provided  for  circulating 
water  through  the  jacket,  the  grinding  wheel  itself  in  this  case 
working  dry.  Suitable  wheel  speeds  and  traverse  feeds  are  provided 
for  the  range  of  work  the  machine  is  designed  to  cover.  Fig.  336 
shows  operation  of  grinding  wrist-pin  bearing,  while  Fig.  337  illus- 
trates charging  the  grinding  jig. 

Flat  Surface  Grinding.  Under  this  heading  properly  comes 
those  machines  designed  for  intensive  production.  These  are  of  two 
distinct  types.  The  one  shown  in  Fig.  338  carries  a  wheel  that 
approaches  the  work  radially,  while  that  shown  in  Fig.  339  uses  the 
side  of  a  cup-shaped  wheel  in  contact  with  the  work.  By  means  of 


280 


MACHINE  SHOP  WORK 


powerful  wheel  driving  belts  and  rapid  table  traverse,  these  machines 
produce  flat  surfaces  with  an  efficiency  and  accuracy  that  leaves 
little  to  be  desired.  The  work  as  shown  is  held  upon  magnetic 
chucks  and  the  throw  of  a  simple  switch  clamps  or  unclamps  it. 
In  use  the  wheel  and  the  work  are  flooded  with  a  suitable  cutting 
lubricant.  In  Fig.  340  are  showrn  a  number  of  gun  parts  finished 


Driving  Pin  Held 
In  Face-Piale 


Driving  Pin  Neb 

t 

s. 

c 

t. 

In  firce-JPlaf-e 

/    Wheel 

s 

\ 

[• 

Vri} 

'/•''v  ;.'-;.  •'•'•'  '••'  .v  • 

:    '•^^^^•T'^ 

,- 

rr 

••'-"•.  '••-.'•'••'".  •••;'•  '''.'•-,' 

;i;-:..\----;-V:;--.;':-: 

'•I.* 

-O.OOO5"~ 

^>                          o.dre"- 
-o.ooos 

—  •» 

xl 
> 

/ 

Center 

L- 

r 

1 

05 

§~~* 

Ci?/ 

?ftr/- 

2>/~iVe/~ 

^2. 

Fig.  333.     Diagram  of  Set-Ups  Shown  in  Figs.  331  and  332 
Courtesy  of  "Machinery",  New  York  City 


WORK: — Main  drive  gear,  0.20  per  cent  carbon  alloy  steel,  carbonized  and 
heat-treated. 

OPERATION: — Straight-in  grinding  external  diameter  with  a  Norton  (vitrified) 
alundum  combination  wneel,  grain  38-24,  grade  L;  20  inches  diameter,  4-i^ch 
lace;  speed,  1241  r.p.m. — 6500  feet  surface  speed;  work  speed,  about  100 
r.p.m. — 41  feet  surface  speed;  amount  removed  from  diameter,  0.010  inch. 

REMARKS: — Wide-face  wheel  is  fed  straight  in  on  portions  (a)  and  (b),  not 
traversed;  small  end  (c)  is  also  ground  in  same  setting  by  shifting  wheel;  pro- 
duction, 265  pieces  in  nine  hours;  machine  used,  10  by  36  inch  Norton  plain  grind- 
ing machine. 

B 

WORK: — Idler  gear  shaft,  0.20  per  cent  carbon  open-hearth  steel,  carbonized 
and  hardened. 

OPERATION: — Straight-in  grinding  two  external  diameters  with  a  Norton 
(vitrified)  alundum  combination  wheel,  grain  38-24,  grade  L;  20  inches  diameter, 
6-inch  face;  speed  1241  r.p.m.— 6500  feet  surface  speed;  work  speed,  100 
r.p.m. — 24  feet  surface  speed;  amount  removed  from  diameter  0.015  to  0.025 
inch. 

REMARKS: — Wide-face  wheel  is  fed  straight  in  on  work,  not  traversed;  50 
pieces  turned  out  to  each  truing  of  wheel;  production,  375  pieces  in  nine  hours; 
machine  used,  10  by  36  inch  Norton  plain  grinding  machine. 


MACHINE  SHOP  WORK 


281 


Fig.  334.     Grinding  Gas  Engine  Cylinders.     View  Shows  Exhaust  for  Dust,  Jig  for  Holding 

Cylinders,  and  Eccentric  Wheel  Spindle 
Courtesy  of  Heald  Machine  Company,  Worcester,  Massachusetts 


Fig.  335.    Grinding  Gas  Engine  Cylinders.     Same  Set-Up  as  Fig.  331,  Showing  Holding  Jig 
and  Turning  Tool  at  Mouth  of  Hole 

by  a  vertical  grinder,  removing  .005  inch  to  .010  inch  of  stock. 
Table  XV  shows  the  number  of  pieces  produced  per  hour. 


282 


MACHINE  SHOP  WORK 


I 


Fig.  337.     Charging  Grinding  Jig  Shown  in  Fig.  336 


Fig.  338.     Example  of  Flat  Surface  Grinding 
Courtesy  of  Norton  Grinding  Company,  Worcester,  Massachusetts 


284 


MACHINE  SHOP  WORK 


TABLE  XV 


Rate  of  Grinding  Gun  Parts 

No  1  on  two  sides —  40  to  50  per  hour 
No.  2  on  one  side  — 125  per  hour 
No.  3  on  one  side  — 175  per  hour 
No.  4  on  two  sides — 100  per  hour 
No.  5  on  one  side  — 150  per  hour 
No.  6  on  two  sides — 150  per  hour 
No.  7  on  two  sides — 175  per  hour 
No.  8  on  two  sides — 200  per  hour 
No.  9  on  two  sides — 200  per  hour 
No.  10  on  two  sides — 200  per  hour 
No.  1 1  on  two  sides — 250  per  hour 
No.  12  on  two  sides — 200  per  hour 


on  Vertical  Grinder 

No.  13  on  two  sides — 175  per  hour 
No.  14  on  two  sides — 200  per  hour 
No.  15  on  two  sides — 200  per  hour 
No.  16  on  two  sides — 175  per  hour 
No.  17  on  two  sides — 100  per  hour 
No.  18  on  two  sides — 125  per  hour 
No.  19  on  two  sides — 200  per  hour 
No.  20  on  two  sides — 150  per  hour 
No.  21  on  two  sides — 150  per  hour 
No.  22  on  two  sides — 100  per  hour 
No.  23  on  two  sides — 150  per  hour 


Fig.  339.     Pratt  and  Whitney  Grinding  Machine  Using  Magnetic  Flat  Chuck 


MACHINE  SHOP  WORK 


285 


/         2         3 


Fig.  340.     Gun  Parts  Ground  on  Vertical  Grinder 

MILLING  MACHINES 

Production  milling  is  done  on  three  distinct  types  of  machines 
known  as  the  horizontal,  the  vertical,  and  the  planer  type. 

Horizontal  Milling  Machine.  Fig.  341  shows  a  representative 
machine  of  this  type.  Designed  and  used  as  shown,  this  machine 
is  capable  of  very  rapid  production.  The  prominent  features  are 
its  weight  and  the  size  of  its  working  parts,  its  large  bearing  surfaces, 
its  all  geared  driving  speed  changes,  its  all  geared  feeds,  and  the 
yoking  of  the  knee  to  the  outer  end  of  the  cutter  arbor. 

Vertical  Milling  Machine.  Fig.  342  is  a  representative  machine 
of  this  type.  While  side  milling  can  be  done  on  this  type  of  machine, 
its  use  is  very  largely  confined  to  the  uses  of  end  and  face  cutting. 
In  common  with  all  high  production  machines,  it  has  weight, 
generous  bearing  surfaces,  large  table  capacity,  great  driving  power, 
and  a  possibility  for  coarse  feeding. 

Planer  Milling  Machine.  The  planer  type  of  milling  machine 
is  the  most  massive  and  the  heaviest  machine  of  the  three  types. 


286 


MACHINE  SHOP  WORK 


A  typical  machine  is  shown  in  Fig.  343.  It  will  be  noted  that  by 
using  side  head  spindles  in  conjunction  with  horizontal  gangs  of 
cutters,  three  or  more  surfaces  may  be  worked  upon  simultaneously. 
Production  Cutters.  It  is  evident  that  the  cutter  equipment 
must  be  equal  to  the  possibilities  of  the  machine  if  its  capacity 
production  is  maintained.  Fig.  344  is  a  characteristic  cutter  used 
in  a  horizontal  milling  machine.  Note  the  large  axial  hole,  making 


Fig..  341.     Horizontal  Milling  Machine  with  Work  in  Process 
Courtesy  of  Cincinnati  Milling  Machine  Company,  Cincinnati,  Ohio 

possible  the  use  of  rigid  arbors,  the  greatly  increased  spacing  of  the 
teeth,  and  the  increased  cutting  rake  given  by  undercutting.  Fig.  345 
shows  the  usual  type  of  cutter  used  when  heavy  slabbing  cuts  are 
taken  in  a  vertical  machine.  The  characteristics  of  coarse  tooth 
pitch,  increased  cutting  rake,  and  rigidity  of  attachment  are  prom- 
inent in  this  cutter.  Either  or  both  of  these  types  of  cutter  are  used 
on  all  three  types  of  machine.  Fig.  346  shows  an  inserted  tooth 
gang  of  Ingersoll  production  cutters  in  actual  operation. 


MACHINE  SHOP  WORK 


287 


Work  Holding.  This  problem  is  usually  cared  for  by  special 
work-holding  devices  termed  "fixtures".  These  fixtures  are  con- 
structed to  grip  and  support  the  work  so  that  the  pressures  and 
thrusts  of  cutting  are  cared  for.  The  fixtures  themselves  are  bolted 
directly  to  the  work  table.  Where  it  can  be  done  quickly  and 


Fig.  342.     Vertical  Milling  Machine  in  Action. '    Work-Holding  Fixture  Rotates 

at  Rate  of  10  Inches  per  Minute;  Production  195  Yokes  per  Hour 
Courtesy  of  Becker  Milling  Machine  Company,  Hyde  Park,  Massachusetts 

conveniently  the  work  is  held  directly  upon  the  work  table.     Mag- 
netic chucks  are  used  to  hold  thin  work. 

Cutting  Speeds.  These  must  be  proportioned  to  the  materials 
being  milled,  their  relative  hardness,  the  depth  of  cut,  and  the  amount 
the  tool  can  be  fed. 


288 


MACHINE  SHOP  WORK 


Fig.  343.     Ingersoll  Horizontal  Milling  Machine,  Milling  Gasoline  Traction  Engine  Fr 
i  Inch  of  Metal  Removed  from  each  of  Six  Surfaces.     14  Bases  Finished  in  10  Hours 


Fig.  344.     Production  Milling  Cutter 
Courtesy  of  Union  Twist  Drill  Company,  Athol,  Massachusetts 


Fig.  3  io.     High-Power  Face  Mill  with  High-Speed  Steel  Teeth 
Courtesy  of  Union  Twist  Drill  Company,  Athol,  Massachusetts 


Fig.  3 16.     Production  Milling  Cutter  in  Heavy  Work 
Courtesy  of  Ingersoll  Milling  Machine  Company,  Rockford,  Illinois 


29C 


MACHINE  SHOP  WORK 


Cutting  Feeds.  These  also  vary  with  working  conditions. 
The  coarsest  practical  feed  is  usually  found  by  experiment  and 
maintained,  bringing  the  cutter  speed  up  to  meet  it. 

Tool  Lubrication.  Cast  iron  is  about  the  only  material  milled 
which  is  cut  "dry".  In  milling  other  metals  and  alloys  a  copious 
supply  of  some  cutting  lubricant  is  used.  This  is  pumped  to  the 
tool  in  quantities  sufficient  to  flood  not  only  the  cutter  but  to  a  large 
extent  the  work.  This  is  well  shown  in  Fig.  347  wrhere  the  cutters 
are  working  on  steel. 

DRILLING   MACHINES 

Production  drilling  machines  are  of  two  sorts:  Those  designed 
for  heavy  drilling,  and  those  for  the  lighter  jobs. 


Fig.  347.     Ingersoll  Horizontal  Miller  Doing  Heavy  Milling 
Note  how  lubricant  floods  the  work  in  milling  steel 

Heavy  High=Speed  Drillers.  Fig.  348  is  fairly  representative 
of  the  type  designed  to  use  high-speed  steel  drills  of  the  larger 
sizes  to  their  full  capacity.  The  frame  or  post  of  this  machine 
is  of  a  form  similar  to  the  frame  of  a  punch  or  shear  press.  Pressure 
tests  on  a  drill  of  IJ-inch  diameter,  given  a  feed  of  0.030  inch  per 
revolution,  have  recorded  a  total  load  pressure  of  nearly  three  tons. 
From  this  it  will  be  seen  why  the  frame  is  made  as  shown.  Feeds 
much  in  excess  of  0.030  inch  can  be  obtained  in  this  machine.  Use 
the  coarsest  feed  practicable  and  balance  the  speed  of  cutting  to  it. 


MACHINE  SHOP  WORK  291 

Light  High=Speed  Drillers.  In  the  lighter  jobs  of  drilling,  a 
feed  exceeding  0.015  inch  per  revolution  is  seldom  used.  Rapid 
production  is  gained  in  this  case  by  maintaining  a  high  cutting 
speed.  Tables  XVI  and  XVII,  published  by  the  Henry  and  Wright 
Company,  show  certain  drilling  practice  where  the  feed  does  not 


Fig.  348.     Baker  Driller  Driving  2^-Inch  Drill  through  Drop-Forged 

Wrought-Iron  Saddles 
Courtesy  of  Baker  Brothers,  Toledo,  Ohio 

exceed  0.016  inch  per  revolution.  Fig.  349  shows  a  power  feed, 
four-spindle  high-speed  driller.  In  designing  this  machine  every- 
thing has  been  done  to  render  its  operation  rapid  and  efficient. 

Special  Drillers.    There  are  many  of  these,  some  of  which  are 
very  complicated.     Fig.  350  shows  a  machine  designed  for  the  single 


292 


MACHINE  SHOP  WORK 


Fig.  349.     Four-Spindle  High-Speed  Bail-Bearing  Sensitive  Driller 
Courtesy  of  Washburn  Shops,  Worcester,  Massachusetts 

purpose  of  drilling  the  clearance  holes  in  threading  dies.  By  using 
four  spindles  and  suitable  work-holding  table  chucks,  a  die  is  com- 
pleted for  each  stroke  of  the  table. 

Production  Figures.  While  there  are  many  records  of  high 
production  drilling,  due  to  the  great  variety  of  drill  work,  it  is 
impossible  to  give  a  table  to  meet  all  needs. 


MACHINE  SHOP  WORK 


293 


TABLE  XVI 
Carbon-Steel  Drills 


SIZE 

OF 

DRILL 
(in.) 

FEED 

PER 

REV. 
(in.) 

BRONZE 
BRASS 
150  FT. 
r.p.m. 

C.  IRON 
ANN'LD 
85  FT. 
r.p.m. 

HARD 
C.  IRON 
40  FT. 
r.p.m. 

MILD 
STEEL 
60  FT. 
r.p.m. 

DROP 
FORG. 
SOFT, 
r.p.m. 

MAL. 
IRON 
45  FT. 
r.p.m. 

TOOL 
STEEL 
30  FT. 
r.p.m. 

CAST 
STEEL 
20  FT. 
r.p.m. 

A 

.003 

5185 

2440 

3660 

1830 

2745 

1830 

1220 

i 

.004 

4575 

2593 

1220 

1830 

915 

1375 

915 

610 

A 

.005 

3050 

1728 

813 

1220 

610 

915 

610 

407 

i 

.006 

2287 

1296 

610 

915 

458 

636 

458 

305 

A 

.007 

1830 

1037 

488 

732 

366 

569 

366 

245 

i 

.008 

1525 

864 

407 

610 

305 

458 

305 

203 

A 

.009 

1307 

741 

349 

523 

261 

392 

261 

174 

.010 

1143 

648 

305 

458 

229 

343 

229 

153 

1 

.011 

915 

519 

244 

366 

183 

275 

183 

122 

T 

.012 

762 

432 

204 

305 

153 

212 

153 

102 

7 

I 

.013 

654 

371 

175 

262 

131 

196 

131 

87 

1 

.014 

571 

323 

153 

229 

115 

172 

115 

77 

U 

.016 

458 

260 

122 

183 

92 

138 

92 

61 

it 

.016 

381 

216 

102 

153 

77 

106 

77 

51 

l| 

.016 

327 

186 

88 

131 

66 

98 

66 

44 

2 

.016 

286 

162 

87 

115 

58 

86 

58 

39 

TABLE  XVII 
High-Speed  Drills 


SIZE 

OF 

DRILL 

(in.) 

FEED 

PER 

REV. 

(in.) 

BRONZE 
BRASS 

300  FT. 

r.p.m. 

C.  IRON 
ANN'LD 

170  FT. 

r.p.m. 

C.  IRON 
HARD 

SOFT. 

r.p.m. 

MILD 

STEEL 

120  FT. 

r.p.m. 

DROP 
FORG. 

60  FT. 

r.p.m. 

MAL. 
IRON 

90  FT. 

r.p.m. 

TOOL 

STEEL 

60  FT. 

r.p.m. 

CAST 
STEEL 

40  FT. 

r.p.m. 

1J6 

.003 

4880 

3660 

3660 

2440 

1 

.004 

5185 

2440 

3660 

1830 

2745 

1830 

1220 

A 

.005 

3456 

1626 

2440 

1210 

1830 

1220 

807 

I 

.006 

4575 

2593 

1220 

1830 

915 

1375 

915 

610 

A 

.007 

3660 

2074 

976 

1464 

732 

1138 

732 

490 

3 

S 

.008 

3050 

1728 

813 

1220 

610 

915 

610 

407 

h 

.009 

2614 

1482 

698 

1046 

522 

784 

522 

348 

\ 

.010 

2287 

1296 

610 

915 

458 

636 

458 

305 

f  ' 

.011 

1830 

1037 

488 

732 

366 

569 

366 

245 

! 

.012 

1525 

864 

407 

610 

305 

458 

305 

203 

7 

1 

.013 

1307 

741 

349 

523 

261 

392 

261 

174 

1 

.014 

1143 

648 

305 

458 

229 

349 

229 

153 

H 

.016 

915 

519 

244 

366 

183 

275 

183 

122 

l| 

.016 

762 

432 

204 

305 

153 

212 

153 

102 

if 

.016 

654 

371 

175 

262 

131 

196 

131 

87 

2 

.016 

571 

323 

153 

229 

115 

172 

115 

77 

Work  Holding.  This  is  usually  accomplished  by  work-holding 
jigs.  These  may  be  held  loosely  upon  the  work  table  or  rigidly 
fastened  to  it  as  their  use  may  warrant.  (See  "Jig-Making".) 


294 


MACHINE  SHOP  WORK 


Lubrication.    Flood  lubrication  of  the  drill  and  the  work  is 
usual  when  production  drilling  upon  metals  other  than  cast  iron, 


Fig.  350.     "Single  Purpose"  Bemis  Driller 


and  tanks,  pumps,  and  a  circulating  system  of  pipes  and  nozzles  are 
provided  on  all  drilling  machines  when  desired  for  this  purpose. 


MACHINE  SHOP  WORK 


295 


1 


SI 

II 

o 


296 


MACHINE  SHOP  WORK 


TURNING  MACHINES 

Special  and  specialized  machines  for  high  speed  turning  will 
be  illustrated  under  this  heading. 

Turning  Lathe.  Fig.  351  shows  a  production  lathe  for  rapid 
turning  of  machine  parts.  It  is  representative  of  its  class.  This 
machine  has  all-geared  drive,  all-geared  feed,  and  is  capable  of 
removing,  when  properly  operated,  several  pounds  of  material  per 
minute  from  such  materials  as  chrome  nickel  steel.  Its  specialized 


1 


Fig.  352.     Tiansparent  View  of  "Reed"  Quick-Change  Gear  Mechanism 

characteristics  are  coarse  feeds,  powerful  driving  capacity,  and  conven- 
ience of  operation.  Fig.  352  is  a  transparent  view  of  the  geared  feed. 
Vertical  Type.  Fig.  353  shows  a  type  of  turning  machine 
in  which  the  work  is  mounted  upon  a  rotating  horizontal  work 
table.  The  advantages  of  this  type  for  certain  classes  of  work  can 
be  readily  seen.  The  tool  holding  heads  are  carried  upon  slides 
and  can  be  fed  both  vertically  and  horizontally.  Boring,  turning, 
facing,  and  threading  can  be  done  on  this  machine.  Its  massive 
construction  and  ease  of  operation  render  it  a  rapid  producer. 
Fig.  354  shows  the  machine  on  some  characteristic  work. 


MACHINE  SHOP  WORK 


297 


Turret  Type.  Where  several  turning  operations  are  to  be 
performed  upon  bar  stock  or  upon  work  held  in  a  chuck,  recourse 
is  often  made  to  the  use  of  a  tool-holding  turret.  Fig.  355  shows 


Fig.  353.     Bullard  Vertical  Turret  Lathe 
Courtesy  of  Bullard  Machine  Tool  Company,  Bridgeport,  Connecticut 


a  horizontal  turret  machine  for  making  machine  parts  from  bar 
stock.  The  cutting  tools  are  fitted  with  shanks  suitable  for  holding 
them  in  the  turret,  and  the  cutting  principle  is  the  same  as  in  all 


298 


MACHINE  SHOP  WORK 


Fig.  354.     Three  Views  of  Bui  lard  Turret  Lathe  in  Action 

On  Piece  Shown,  Time  Required  for  Setting  Tools,  Turning,  Chamfering,  Boring,  and 
Finishing,  80  Minutes. 

Courtesy  of  "Machinery",  New  York  City 

cutting  tools.  Both  long  and 
short  turning  can  be  done  in  this 
machine.  The  turret  provides  for 
six  tools. 

Fig.  356  shows  a  similar  ma- 
chine designed  to  handle  iron 
or  steel  castings.  This  machine 
when  properly  tooled  up,  will 
perform  turning  and  boring 


Fig.  355a.    Diagram  Showing  Piece  Producted 
by  Turret  Lathe,  Fig.  355b 


MACHINE  SHOP  WORK 


299 


300 


MACHINE  SHOP  WORK 


MACHINE  SHOP  WORK 


301 


I 

II 


302 


MACHINE  SHOP  WORK 


MACHINE  SHOP  WORK  303 

operations  upon  a  large  variety  of  parts.  The  fundamental  cutting 
principle  is  maintained  in  its  tooling.  It  is  an  efficient  producer. 

"Lo-Swing"  Type.  Fig.  357  shows  a  highly  specialized  turning 
machine  in  which  a  train  of  cutting  tools  may  be  operated.  Rough- 
ing out  spindles  is  a  particular  function  of  this  machine.  Fig.  358 
illustrates  a  typical  "lo-swing"  job. 

Lubrication.  All  production  turning  machines  may  be,  when 
desired,  equipped  with  a  lubrication  system  to  flood  the  cutting 
tool  with  either  oil  or  compound. 

Cutting  Speeds  and  Feeds.  All  these  machines  are  designed 
to  work  any  cutting  tool  to  the  limit  of  its  endurance. 


Fig.  359.     Cleveland  Automatic 
Courtesy  of  Cleveland  Automatic  Machine  Company,  Cleveland,  Ohio 

Automatics.  The  term  "automatic' *  designates  a  line  of 
machines,  in  which,  when  once  properly  tooled  and  adjusted,  the 
functions  of  the  machine  are  to  a  considerable  extent  automatic 
in  their  action.  By  means  of  cam  movements,  and  link  and 
crank  motions,  the  cutting  tools  and  the  work  are  made  to  func- 
tion as  desired.  In  Figs.  359,  360,  and  361  are  shown  representa- 
tive automatics. 

Uses  of  Automatics.  The  broadest  use  of  such  machines  is 
upon  work  which,  besides  being  turned,  is  also  drilled  and  perhaps 
threaded.  The  automatic  shown  in  Fig.  359  is  for  heavy  work  and 
takes  through  its  work  spindle,  bar  stock  several  inches  in  diameter. 
The  bar  is  worked  upon  by  both  turret  and  cross-slide  cutting  tools. 


304 


MACHINE  SHOP  WORK 


The  tool  turret  is  fed  by  a  cylindrical  cam  grooved  to  give  a  powerful 
feed.  The  machine  can  be  functioned  to  complete  a  piece  in  one 
cycle  of  the  machine.  As  the  finished  part  is  dropped,  the  work 
bar  is  automatically  advanced  to  receive  another  tooling,  and  goes 
through  the  same  cycle  of  operations. 

Fig.  360  is  representative  of  a  type  of  machine  used  in  turning 
and  boring  special  castings.  Like  other  automatics  the  cutting 
tools  are  held  in  turrets,  and  are  automatically  rotated  into  position 
and  advanced  by  cam  movements. 


Fig.  360.     Typical  Automatic  Turning  and  Boring  Special  Castings 

Fig.  361  shows  a  machine  used  largely  in  producing  the  smaller 
machine  parts,  as,  for  example,  the  smaller  screws,  studs,  collars, 
sleeves,  etc.,  used  in  machine  construction. 

The  automatic  shown  in  Fig.  362  is  designed  for  producing 
work  similar  to  that  produced  by  the  machine,  Fig.  361.  It,  how- 
ever, is  provided  with  five  work  spindles.  The  five  feed  tubes  are 
shown  at  the  left. 

Lubrication.  Automatics  such  as  those  shown  are  provided 
with  stream  or  flood  lubrication  systems. 


MACHINE  SHOP  WORK 


305 


306 


MACHINE  SHOP  WORK 


PLANING  MACHINES 

Production  Planers.  The  machine  tool  shown  in  Fig.  363  is  for 
quantity  production  of  plane  surfaces.  Enormous  machines  of  this 
type  are  in  use,  constructed  to  drive  and  feed  the  best  of  cutting  tools 


MACHINE  SHOP  WORK 


307 


to  their  endurance  limits.     By  the  use  of  several  tool-carrying  heads 
tooling  can  be  done  on  the  top  and  the  side  surfaces  simultaneously. 


ll 


CO     g 

.ail 
fe  ,s 


Work  Holding.     In  the  case  of  production  work,  where  size 
precludes   the   mounting   of   more   than   a   single    piece    on    the 


308 


MACHINE  SHOP  WORK 


work  table,  the  work  usually  rests  on  the  table  itself  without  sup- 
porting fixtures.     In  locating  the  work  and  holding  it  true  to  its 


location,  a  variety  of  bolts,  straps,  thrust  blocks,  angle  irons,  and 
struts  are  usually  available.    Where  the  size  of  the  work  warrants 


MACHINE  SHOP  WORK 


309 


mounting  more  than  a  single  piece  upon  the  work  table,  work-holding 
fixtures,  as  shown  in  Fig.  364,  are  usually  provided.  These  may 
also,  by  design,  accurately  locate  the  pieces. 

Lubrication.     In  planer  work,  the  cutting  tool  is  seldom  lubri- 
cated. 

BROACHING  MACHINES 

Types  of  Machines  and  Nature  of  Work.    Fig.  365  is  repre- 
sentative of  a  type  of  machine  tool  which  makes  use  of  a  train  of 


Fig.  365.     Typical  Broaching  Machine 
Courtesy  of  LaPointe  Machine  Tool  Company,  Hudson,  Massachusetts 

cutting  edges  for  roughing  and  finishing  holes  in  machine  parts. 
Typical  broaches  are  shown  in  Fig.  366.  The  cutting  edges  are 
usually  formed  as  an  integral  part  of  .the  broach  itself. 

Operation.  The  leading  end  of  the  broach  is  passed  through 
the  previously  drilled  or  cored  hole  in  the  piece  of  work,  and  is 
attached  to  the  power  or  work  spindle.  This  spindle,  as  shown  in 


310 


MACHINE  SHOP  WORK 


Fig.  366.     Typical  Broaches 
Courtesy  of  LaPointe  Machine  Tool  Company,  Hudson,  Massachusetts 

Fig.  365,  is  a  threaded  bar  running  in  a  suitable  frame.  The  driving 
mechanism  screws  the  threaded  spindle  along  the  axis  of  the  machine 
until  the  broach  has  been  pulled  through  the  hole  in  the  work. 

Work  Holding.  The  work  is  held  Against  a  footing  block  which 
resists  the  thrust  due  to  the  pull  of  the  broach. 

Lubrication.  As  the  speed  of  cutting  is  comparatively  slow,  the 
cutting  lubricant  may  be  applied  with  a  brush  or  by  use  of  a  drip  can. 

Production.  Holes  having  other  than  a  circular  form  are 
the  particular  province  of  the  broaching  machine.  Fig.  367  shows 
some  typical  holes  and  Table  XVIII  gives  rates  of  production. 

TABLE  XVIII 
Data  on  Rates  of  Production  with  Different  Broaching  Machines* 

NOTE.     Numbers  refer  to  Fig.  367.  - 

No.  1.  HEXAGON  HOLE  WITH  ONE  ROUND  SIDE.  Distance  across  flats 
11  in.,  length  1£  in.,  material  steel.  No.  2  Machine.  Production  45  pieces  per 
hour. 


*  Courtesy  of  LaPointe  Machine  Tool  Company.  Hudson,  Massachusetts. 


MACHINE  SHOP  WORK  311 

No.  2.  FOUR  SPLINES.  Hole  If  in.  diameter,  splines  f  in.  X  TS~  in., 
2i  in.  long,  material  steel.  No.  3  Machine.  Production  20  pieces  per  hour. 

No.  3.  SQUARE  HOLE.  Distance  across  flats  1  in.,  1£  in.  long,  material 
steel.  No.  2  Machine.  Production  40  pieces  per  hour. 

No.  4.  FOUR  SPIRAL  KEYS.  Diameter  of  hole  1  in.,  keys  £  in.  X  £  in., 
2  in.  long,  material  steel.  No.  3  Machine.  Production  15  pieces  per  hour. 

No.  5.  CLUTCH  USED  ON  MINING  MACHINERY.  Diameter  of  hole  2|  in. 
Double  depth  of  slots  3|  in.,  length  2  in.,  material  steel.  No.  3  Machine.  Pro- 
duction 20  pieces  per  hour. 

No.  6.  SOLID  KEY.  Taken  from  1|  in.  round  hole,  leaving  solid  key 
\  in.  X  i  in.,  length  2^  in.,  material  steel.  No.  3  Machine.  Production  15 
pieces  per  hour. 

No.  7.  Six  RADIAL  SPLINES.  Diameter  of  hole  2|  in.,  splines  f  in.  X  1  in., 
2 1  in.  long,  material  steel.  No.  3  Machine.  Production  20  pieces  per  hour. 

No.  8.  HOUSING  FOR  BRONZE  BEARINGS.  Openings  4|  in.  X  H  in.,  2  in. 
through,  material  C.  I.  No.  3  Machine.  Production  from  rough  casting  20 
pieces  per  hour. 

No.  9.  SQUARE  HOLE.  Distance  across  flats  2  in.,  length  3|  in.,  material 
steel.  No.  3  Machine.  Production  from  a  drilled  hole,  15  pieces  per  hour. 

No.  10.  SQUARE  HOLE.  Distance  across  flats  3  in.,  length  4  in.,  material 
steel.  No.  4  Machine.  Production  from  drilled  hole,  15  pieces  per  hour. 

No.  11.  THREE  DOVETAIL  SPLINES.  Diameter  of  hole  If  in.,  splines 
1  in.  X  i^  in.,  2  in.  long,  material  brass.  No.  3  Machine.  Production  45  pieces 
per  hour. 

No.  12.  EIGHT  DOVETAIL  SPLINES.  Diameter  of  hole  3|  in.,  splines 
f  in.  X  i^  in.,  3  in.  long,  material  steel.  No.  4  Machine.  Production  15  pieces 
per  hour. 

No.  13.  SQUARE  HOLE.  If  in.  across  flats,  5  in.  long,  material  steel. 
No.  3  Machine.  Production  from  drilled  hole,  15  pieces  per  hour. 

No.  14.  UNIVERSAL  JOINT  PART.  Hole  2^  in.  across  flats,  f  in.  through, 
material  C.  I.  No.  3  Machine.  Production  30  pieces  per  hour. 

No.  15.  BABBITT  BEARING.  Diameter  2  in.,  length  2J  in.  Broached  to 
exact  size,  compressed  and  burnished.  No.  3  Machine.  Production  60  pieces 
per  hour.- 

No.  16.  ROUND  HOLE.  3  in.  diameter,  4f  in.  long,  material  C.  I.  No.  3 
Machine.  Production  from  cored  hole  30  pieces  per  hour. 

No.  17.  CRUCIFORM  USED  IN  MINING  MACHINERY.  Splines  £  in.  X  I  in., 
7  in.  long,  material  steel.  No.  3  Machine.  Production  from  f  in.  round  hole, 
7  pieces  per  hour. 

No.  18.  OVAL  SHAPED  HOLES,  yf  in.  X  I  in.,  J  in.  through,  material 
steel.  No.  2  Machine.  Production  approximately  600  holes  per  hour. 

No.  19.  REVOLVER  FRAME.  Size  of  hole  for  chamber  If!  in.  X  1|  in., 
f  in.  through,  material  steel.  No.  2  Machine.  Production  from  rough  forging 
20  pieces  per  hour. 

No.  20.  HEXAGON  HOLE.  Distance  across  flats  2f  in.,  2|  in.  long,  material 
steel.  No.  3  Machine.  Production  from  drilled  hole  40  pieces  per  hour. 

No.  21.  TWO-SPLINE  HOLE,  l&  in.  X  TS  in.,  3|  in.  long,  material  steel. 
No.  2  Machine.  Production  from  f  in.  drilled  hole,  10  pieces  per  hour. 


Fig.  367.    Samples  of  Broaching  Work 
Courtesy  of  LaPointe  Machine  Tool  Company,  Hudson,  Massachusetts 


MACHINE  SHOP  WORK  313 

No.  22.  HOLE.  \  in.  X  i^  in-,  \  in.  long,  material  steel.  No.  1  Machine. 
Production  from  drilled  hole  25  pieces  per  hour. 

No.  23.  SQUARE  HOLE.  \  in.  across  flats,  2  in.  long,  material  steel.  No.  1 
Machine.  Production  from  drilled  hole  20  pieces  per  hour. 

No.  24.  PEAR  SHAPED  HOLE.  Diameter  of  round  broach  1  in.,  If  in.  long, 
material  steel.  No.  2  Machine.  Production  20  pieces  per  hour. 

No.  25.  INTERNAL  GEAR.  Hole  lj  in.,  1|  in.  long,  15  teeth,  material 
steel.  No.  3  Machine.  Production  from  drilled  hole  40  pieces  per  hour. 

No.  26.  INTERNAL  RATCHET  140  TEETH.  Diameter  of  hole  1  in.,  length 
\\  in.,  material  steel.  No.  2  Machine.  Production  45  pieces  per  hour. 

No.  27.  Six  SPLINES.  Diameter  of  hole  2f  in.,  splines  f  in.  X  I  in.,  1  in. 
long,  material  drop-forged  steel.  No.  4  Machine.  Production  35  pieces  per  hour. 

No.  28.  BRONZE  BUSHING.  Hole  rf  in.  diameter,  1|  in.  long.  No.  3 
Machine.  Broached  to  exact  size,  compressed  and  burnished.  Production 
from  cored  hole  100  pieces  per  hour. 

No.  29.  MAGNETO  COUPLING.  Hole  If  in.  diameter,  \  in.  long,  20  teeth, 
material  steel.  No.  3  Machine.  Production  from  drilled  hole  90  pieces  per 
hour. 

No.  30.  Two  SPIRAL  KEYWAYS.  Diameter  of  hole  2  in.,  keyways 
|  in.  X  I  in.,  1|  in.  long,  material  steel.  No.  3  Machine.  Production  40  pieces 
per  hour. 

No.  31.  TEN  SPLINES.  Diameter  of  hole  If  in.,  splines  J  in.  X  I  in., 
lj  in.  long,  material  steel.  No.  3  Machine.  Production  45  pieces  per  hour. 

No.  32.  TOOL  STEEL  DIE  FOR  PRESSING  TIN  TOP  ON  BOTTLES.  Diameter 
of  hole  1  iV  in.,  |  in.  long,  21  teeth.  No.  2  Machine.  Production  from  drilled 
hole  60  pieces  per  hour. 

No.  33.  FOUR  SPLINE.  Diameter  of  hole  \\  in.,  splines  ^  in.  X  \  in. 
1?  in.  long,  material  steel.  No.  2  Machine.  Production  45  pieces  per  hour. 

No.  34.  TAPER  SQUARE  HOLE.  Distance  across  flats,  small  end,  \\  in., 
large  end  \\  in.,  2  in.  long,  material  steel.  No.  2  Machine.  Production  12 
pieces  per  hour. 

No.  35.  FOUR  SOLID  KEYS.  Diameter  of  hole  ITS  in.,  keys  fV  in.  X  \  in., 
If  in.  long,  material  steel.  No.  3  Machine.  Production  20  pieces  per  hour. 

No.  36.  BUSHING  FOR  .TROLLEY  WHEEL.  Diameter  of  hole  \  in.,  six 
spiral  keyways  \  in.  X  rV  in.,  1|  in.  long,  material  bronze.  No.  2  Machine. 
Production  100  pieces  per  hour. 

No.  37.  FOUR  SPLINES  IN  TAPER  HOLE.  Hole  \  in.  diameter  at  small 
end,  f  in.  diameter  at  large  end,  splines  \  in.  X  re  in.,  \  in.  long.  Splines  parallel 
with  taper,  material  steel.  No.  1  Machine.  Production  25  pieces  per  hour. 

No.  38.  FOUR  SPLINES.  Diameter  of  hole  f  in.,  splines  i  in.  X  J  in., 
|  in.  long,  material  steel.  No.  1  Machine.  Production  15  pieces  per  hour. 

No.  39.  SINGLE  KEYWAY.  Diameter  of  hole  \  in.,  keyway  ^  in.  X  r&  in., 
f  in.  long,  material  brass.  No.  1  Machine.  Production  approximately  250 
pieces  per  hour. 

No.  40.  SINGLE  KEYWAY.  Diameter  of  hole  f  in.,  keyway  rV  in.  X  -h  in., 
1  in.  long,  material  steel.  No.  1  Machine.  Production  160  pieces  per  hour. 


314  MACHINE  SHOP  WORK 

PRODUCTION  TOOLS,  JIGS,  AND  FIXTURES 
CUTTING  TOOLS 

Materials.  Iron.  Iron  is  one  of  the  commonest  metals  in 
use.  In  nature  it  is  found  in  a  form  known  as  iron  ore.  In  this 
form  it  has  many  impurities  from  which  it  must  be  separated  before 
it  is  valuable  as  an  article  of  commerce.  By  well-known  methods 
commercially  pure  iron  is  obtained  from  the  iron  ore.  Combining 
this  commercially  pure  iron  with  other  ingredients  under  well-known 
methods  of  heating,  the  various  grades  of  steels  are  produced. 

Tool  Steel.  For  generations  cutting  tools  as  used  in  machine 
shop  practice  have  been  made  from  that  grade  of  steel  commercially 
known  as  tool  steel,  the  principal  constituents  of  which  are  pure 
iron  and  carbon.  In  recent  years,  the  metallurgist  has  combined 
other  metals  with  iron  to  produce  steels  suitable  for  cutting  tools, 
which  have  in  many  cases  superseded  the  older  grades  of  tool  steel. 
To  distinguish  the  older  grades  from  the  newer,  the  former  are  now 
generally  termed  carbon  tool  steels  or  simply  carbon  steels.  In 
all  the  steels  iron  is  the  principal  constituent.  For  example,  carbon 
tool  steel  may  have  less  than  one  per  cent  of  carbon  in  its  make-up 
and  seldom  has  to  exceed  1.250  per  cent  of  carbon  for  ordinary 
shop  cutting  tools.  In  designating  percentages  of  constituents, 
the  steel-maker  and  user  usually  refers  to  them  as  so  many  "points". 
For  example,  instead  of  saying  that  a  certain  steel  has  eighty  hun- 
dredths  of  one  per  cent  of  carbon,  he  would  say  that  the  steel  was 
eighty  point  carbon;  this  is  usually  written  "80  point".  All  tool 
steels  have  the  peculiar  quality  of  acquiring  an  intense  hardness 
when  heated  to  the  requisite  degree  of  temperature  and  then  cooled 
suddenly.  If  this  is  properly  and  scientifically  done,  a  beautiful 
cutting  quality  results.  The  older  carbon  steel  cutting  tool  has 
this  weakness,  however,  that  it  loses  its  hardness  at  a  comparatively 
low  cutting  temperature.  As  rapid  metal  cutting  generates  con- 
siderable quantities  of  heat,  this  tendency  of  the  carbon  steel  cutting 
tool  to  lose  its  extreme  hardness  precludes  rapid  cutting  and  holds 
the  operator  to  low  cutting  speeds.  A  glance  at  the  accompanying 
speed  tables  clearly  shows  this. 

High-Speed  Steel.     In  1894  and  1895,  Messrs.  Taylor  and  White 
sought  by  experiment  to  produce  a  steel  for  cutting  tools  which 


MACHINE  SHOP  WORK 


315 


would  show  a  greater  cutting  efficiency  in  the  shop.  They  finally 
developed  the  so-called  Taylor  and  White  high-speed  steel,  the 
forerunner  of  numerous  brands  of  high  speed  steels.  Cutting  tools 


Fig.  368.     Taylor  Standard  Cutting  Contours 
Courtesy  of  Ready  Tool  Company,  Bridgeport,  Connecticut 


made  from  these  steels  have  the  peculiar  quality  of  retaining  their 
hardness  at  cutting  temperatures  much  in  excess  of  those  sustained 
by  tools  made  from  carbon  tool  steel.  For  this  reason  cutting  speeds 
have  been  materially  increased.  It  is  well  to  understand  that  the 
increased  speed  of  cutting  is  not  due  to  the  new  steels  taking  a  greater 
hardness  when  heat  treated,  than  the  older  steels,  simply  that 
they  retain  their  hardness  at  temperatures  which  soften  the  cutting 
edges  of  carbon  steel  cutting  tools  to  such 
an  extent  that  their  keenness  is  lost. 

Production  Tools.  In  Machine  Shop 
Work,  Parts  I-IV,  the  usual  cutting  tools 
have  been  treated.  We  will  now  discuss  the 
more  specialized  forms  used  in  production 
machine  work. 

Turning  Tools.  Fig.  368  shows  diagram- 
matically  the  Taylor  form  of  cutting  tools  Fig.  369.  Red-E  standard 

Cutting  Contours 

as  used  for  rough  and  for  finish  turning. 

Fig.  369  shows  these  as  modified  by  one  manufacturer  of  lathe  tool 
holders.  Cutting  tools  shaped  to  these  contours  are  much  used  in 
production  turning.  Fig.  373  shows  how  the  tool  approaches  its  cut. 


316 


MACHINE  SHOP  WORK 


As  all  cutting  is  a  process  of  splitting  it  is  very  important 
that  the  cutting  tool  be  properly  set  up  as  relates  to  its  cut. 


Fig.  370.     Red-E  Roughing  Tool 
Courtesy  of  Ready  Tool  Company,  Bridgeport,  Connecticut 

Fig.  327  illustrates  the  kind  of  surface  these  tools  produce 
when  correctly  used. 

Planing  Tools.  The  set  of  tools  shown  in  Fig.  371  are  cor- 
rectly ground  for  planer  use.  Due  to  the  nature  of  their  use,  planer 
tools  are  necessarily  of  many  contours.  Their  use  is  well  illus- 
trated in  Fig.  372. 

Milling  Tools.  The  older  type  of  milling  cutter  with  its  finer 
pitched  teeth  does  not  work  well  under  production  conditions 
of  coarse  feeding  and  heavy  cuts.  Coarse  pitch  cutters  with  maxi- 


Fig.  371.     Set  of  Planer  Tools  Ground  on  Sellers'  Tool-Grinding  Machine 
Courtesy  of  "Machinery",  New  York  City 

mum  chip  space  between  the  teeth  are  now  universally  used  in 
production  milling.  Fig.  346  shows  a  milling  cutter  which  is  con- 
structed especially  for  coarse  feeds  and  heavy  cuts. 


Fig.  372.     Planer  Tools  of  Different  Form  and  Work  to  Which  They  Are"  Adapted 
Courtesy  of  "Machinery",  New  York  City 


Fig.  373.     Right  and  Wrong  Method  of  Feeding  Lubricant  to  Cutting  Tool 
Courtesy  of  "Machinery",  New  York  Cife' 


318 


MACHINE  SHOP  WORK 


*  Drilling  Tools.  High-speed  drills  for ,  production  are  shown 
in  Figs.  348  and  349.  In  experimental  tests  on  cast  iron,  drills 
made  from  high-speed  steel  are  reported  to  have  been  fed  yV  inch 
per  revolution  and  at  a  cutting  speed  sufficiently  high  to  give  a 
hole  depth  of  about  60  inches  per  minute. 

Cutting  Lubrication.  Lubrication  of  the  cutting  tool  is  com- 
mon when  production  cutting  is  being  done  upon  wrought  iron  or 

steel.  It  has  been  found 
that  at  times  an  increased 
production  of  nearly  50  per 
cent  can  be  obtained  by 
forcing  a  heavy  stream  of 
cutting  lubricant  upon  the 
cutting  tool  at  the  point 
where  the  metal  is  being  sep- 
arated. The  lubricant  ap- 
pears to  be  most  effective 
when  it  reaches  the  cutting 
edge  at  a  slow  velocity  and 
in  sufficient  quantities  to 
submerge  the  tool  at  the 
point  of  contact.  Fig.  373 
shows  diagrammatically 
right  and  wrong  methods  of 
application. 

In  Fig.  338  the  grind- 
ing wTheel  is  nearly  hidden 
by  the  flood  of  lubricant 
and  Fig.  374  shows  how  gen- 
erously the  cutting  lubricant 
is  flooded  to  a  drill  when 
cutting  steel. 

Lubricants.  The  common  cutting  lubricants  used  in  heavy 
machining  operations  are  lard  oil,  mixtures  of  lard  oil  and  paraffin 
oil,  and  the  various  mixtures  of  water,  oil,  soft  soap,  and  sal  soda, 
commonly  termed  "compounds".  Several  mixtures  of  this  sort 
are  sold  under  specific  trade  names. 

Most  of  the  modern  manufacturing  machine  tools  are  provided 


Fig.  374.     Drilling  Operation  Showing  How 

Lubricant  Floods  the  Work 
Courtesy  of  "Machinery",  New  York  City 


MACHINE  SHOP  WORK  319 

with  a  system  for  handling  the  cutting  lubricant  in  large  quantities. 
This  usually  consists  of  a  supply  tank  with  a  settling  chamber,  an 
effective  geared  pump,  and  the  distributing  pipes. 

JIGS  AND  FIXTURES 

General  Classification.  The  terms  "jigs"  and  "fixtures"  are 
rather  loosely  used  by  shopmen.  While  this  is  necessarily  so  in 
some  cases,  in  most  instances  it  is  more  correct  to  apply  the  term 
jig  to  a  device  which  holds  the  work  and  automatically  locates 
the  cutting  tool  so  that  each  piece  produced  is  a  duplicate  of  all 
the  others.  Fixtures,  on  the  other  hand,  do  not  automatically 
locate  the  cutting  tool.  While  fixtures  may  be  used  to  produce 
duplicates,  this  result  is  usually  gained  by  means  of  a  cutting  tool 
locating  jig  separated  from  the  fixture  itself.  Fixtures  are  essen- 
tially work-holding  devices. 

Object  of  These  Tools.  While  several  effects  are  gained  by 
using  jigs  and  fixtures,  they  all  reduce  to  one  thing,  namely,  pro- 
duction. For  example,  by  the  proper  use  of  jigs  and  fixtures,  pro- 
duction is  made  more  uniform,  giving  interchangeability  of  parts. 
If  jigs  and  fixtures  are  properly  used,  production  is  attended  by  a 
reduction  of  labor  cost,  both  wrhen  the  machine  parts  are  being 
produced,  and  when  the  parts  are  assembled  to  produce  the  com- 
pleted machine. 

Importance.    That  jigs  and  fixtures  are  an  important  factor 

in  modern  production  is  clearly  shown  by  a  study  of  the  various 

•production  cuts  in  this  book.     These  illustrations  for  the  most 

part  show  the   machine  in  a  working  condition,  and  in  nearly  every 

case  some  special  fixture  or  jig  is  holding  the  work  or  is  guiding 

the  tool.     In  some  cases,  the  special  work-holding  device  is  a  simple 

\  work  chuck  or  a  magnetic  work  chuck,  in  others  the  special  devices 

Vdb  rather  elaborate. 

Jig  Design  and  Construction 

Many  of  the  rules  governing  jig  design  hold  true  for  fixtures, 
d  jig  design  will  be  taken  up  first. 

Fundamental  Principles  of  Design.  Use  of  Jig.  In  jig  design 
it  is  usual  to  first  consider  the  uses  to  which  it  is  to  be  put.  If,  for 
example,  the  piece  for  which  the  jig  is  made  is  to  finally  bear  a 


320  MACHINE  SHOP  WORK 

fixed  relation  to  some  other  machine  part,  it  becomes  necessary  to 
consider  not  only  the  part  being  jigged,  but  also  its  relation  to  the 
other  parts  with  which  it  is  to  be  assembled.  Again,  if  the  piece 
being  jigged  is  of  special  accuracy,  the  jig  design  may  be  different 
from  that  of  a  machine  part  in  which  no  special  accuracy  is  re- 
quired. In  one  case,  the  jig  is  both  a  rapid  production  tool  and  an 
interchangeability  tool.  In  the  other  case,  the  jig  is  merely  a  con- 
venient tool  for  getting  rapid  production. 

As  a  Work  Holder.  It  is  usual  in  the  design  of  jigs  to  next 
consider  how  the  piece  shall  be  held  in  the  prospective  jig.  The 
points  or  surfaces  upon  the  piece  which  are  those  best  suited  for 
location  points  and  surfaces  are  decided  upon.  If  the  piece  has  been 
previously  machined,  the  surface  machined  usually  offers  the  best 
location  to  work  from.  If,  on  the  other  hand,  the  surfaces  of  the 
stock  are  rough,  as  in  an  ordinary  casting,  the  selection  of  the  locat- 
ing surfaces  or  surface  is  usually  a  more  difficult  one.  Usually 
some  surface  or  hole  will  be  essentially  more  important  than  all 
the  remaining  surfaces  or  holes.  In  such  a  case,  the  jig  designer 
uses  location  points  which  will  position  the  important  hole  or  sur- 
face, afterward  considering  the  points  of  lesser  importance.  This 
he  terms  "working  to  or  working  from  the  important  point".  A 
flat  surface,  if  it  has  previously  been  machined,  is  usually  located 
against  a  flat  surface;  if  not  previously  machined,  a  flat  surface 
should  be  given  line  or  point  contact.  It  is  customary  to  locate 
a  curved  surface  against  a  V  or  against  points. 

Clamping.  This  refers  to  the  particular  devices  which  hold 
the  piece  being  jigged  against  the  location  points  or  surfaces.  The 
design  should  be  such  that  the  least  number  of  clamping  devices 
may  be  used,  so  that  no  unnecessary  time  is  consumed  in  charging 
the  jig,  as  this  limits  production  unless  the  jigs  are  charged  as  a 
separate  job. 

All  clamping  devices  should  exert  their  pressure,  wherever 
possible,  directly  in  line  with  the  supporting  points.  If  this  is  done 
the  piece  clamped  will  not  be  sprung  out  of  shape.  As  an  aid 
in  understanding  the  already  mentioned  points,  a  simple  jig  will 
be  illustrated  and  its  construction  described. 

Drill  Jigs.  While  a  study  of  the  illustrations  in  this  book 
will  show  the  student  that  jigs  are  an  important  factor  in  all  pro- 


MACHINE  SHOP  WORK 


321 


duction  machines,  perhaps  in  no  other  machine  is  their  importance 
so  complete  as  in  the  drilling  of  holes.  For  this  reason  a  drill  jig 
will  be  used  to  illustrate  jig  construction.  In  the  line  drawing, 
Figs.  375  and  376,  are 
shown  the  top  and  bottom 
views  of  a  simple  jig  of  the 
open  box  type  designed  to 
rapidly  produce  duplicate 
work.  In  Fig.  377  are 
shown  two  views1  of  a  jig 
of  the  closed  box  type  for 
rapid  production  of  dupli- 
cate parts.  While  neither 
of  these  jigs  are  elaborate 
in  either  design  or  construction,  they  fairly  represent  their  types. 
Types  of  Drill  Jigs.  Drill  jigs  are  of  three  forms  (a)  plate 
jigs;  (b)  open  box;  (c)  closed  box.  The  plate  jig  usually  consists 


Fig.  375.     Typical  Open  Box  Drill  Jig 
Courtesy  of  "American  Machinist" 


Fig.  376.     Bottom  View  of  Box  Drill  Jig  Shown  in  Fig.  375 
Courtesy  of  "American  Machinist" 

of  a  flat  plate  with  located  bushings  which  is  positioned  on  the  work 
and  clamped  to  it.  The  open  box  type,  as  shown  in  Figs.  375  and 
376,  consists  of  a  casting  provided  with  legs  or  feet.  The  piece 
jigged  is  clamped  to  the  lower  or  under  surface  of  the  jig  body. 


322 


MACHINE  SHOP  WORK 


The  closed  box  type  is  such  that  the  piece  to  be  jigged  is  positioned 
in  a  box  which  may  be  entirely  or  partially  closed.     In  the  lower 

view,  Fig.  377,  the  box, 
as  shown,  is  open  on  one 
side  and  partially  so  on 
another  side. 

Locating  Work  in 
Drill  Jigs.  Fig.  378  shows 
the  use  of  pins  or  studs 
used  as  side-locating  points 
in  simple  jig  work,  and 
Fig.  379  shows  how  V's 
are  similarly  used  on 


Fig.  377.     Two  Views  of  Closed  Box  Drill  Jig 
Courtesy  of  "American  Machinist" 


curved  surfaces.     While  these  are  simple  examples,  they  illustrate  a 
principle  which  can  easily  be  applied  to  more  complicated  cases. 


MACHINE  SHOP  WORK 


323 


The  use  of  locating  pads  is  shown  in  Fig.  380,  and  Fig.  381 
shows  how  an  inserted  pin  may  be  used  for  supporting  a  plane 
surface.     Where  pins  are  used  for  location  points,  Fig.  378,  the  sides 
against  which  the  pieces  are 
located    are   usually    flatted 
somewhat   to   bring   surface 
contact  rather  than  line  con- 
tact.     Hardening  the  pins  will       Fig.  378.     Method  of  Using  Locating  Stub?  or  Pins 

also  prevent  excessive  wear. 

Locating  Points  with  Adjustments.  In  some  cases,  it  is  well 
to  have  locating  surfaces  or  points  adjustable.  In  Fig.  381  the 
inserted  pin,  if  threaded  into  base  B  could,  for  example,  be  raised 
to  some  other  position  from  that  shown.  Some  jig  designers, 
instead  of  the  V-block  shown  in  Fig.  379,  use  two  set  screws  hor- 
izontally set  at  an  angle  of  45  degrees  with  one  another,  bringing 
the  curved  surface  against  their  points. 

Clamping.  This  is  done  in  a  great  variety  of  ways  and  many 
of  the  devices  are  very  ingenious.  However,  they  nearly  all  reduce 
to  some  form  of  clamp  either  straight,  bent,  or  forked,  pressed  against 
the  work  by  either  a  set  screw,  a  cap  screw,  or  a  cam.  In  Fig.  375 
it  will  be  noted  that  the  clamping  is  done  by  a  strap  similar  to  that 
shown  in  Fig.  382,  and  the  piece  is  pushed  into  position  by  knurled 
head  set  screws.  In  Fig.  377  set  screws  are  used,  supplemented 


'  adjustable  V  Block 


I    I 


I  I 


I  I 


Fig.  379.     Diagrams  Showing  Fixed  and  Adjustable  V's 

by  a  swinging-wing  clamp  at  the  side  pressing  against  the  piece 

of  work.     Fig.  383  shows  favorite  forms  of  cam  clamping  devices. 

Jig  Body.    While  steel  may  be  used  for  the  body  or  frame  of 

a  jig,  it  is  a  usual  thing  to  use  cast  iron.     If  cast  iron  is  used  the  jig 


324 


MACHINE  SHOP  WORK 


can  be  more  or  less  completely  worked  out  in  the  pattern,  and 
possibilities  of  alteration  in  design  may  show  as  desirable.  When 
it  is  realized  that  many  shops  use  jigs  weighing  hundreds  of  pounds 


Pad 


Pad 


Pad 


Fig.  380.     Diagram  Showing  Use  of  Locating  Pads 


Fig.  381.     Sketch  Showing  Adjustable  Locating  Points 


in  their  production  work,  it 
is  clearly  seen  wrhy  cast  iron 
is  largely  used  for  jig  bodies. 
Bearing  Points.  Only  in 
the  smaller  sizes  do  drill  jigs 
rest  upon  a  surface  of  any 
considerable  area.  It  will  be 
noted,  by  reference  to  Figs. 
375,  376,  and  377,  that  supporting  points,  termed  feet,  are  pro- 
vided on  those  sides  of  the  jig  which  are  to  rest  upon  the  work 
table.  The  height  of  the  feet  must  be  sufficient  to  clear  all  bushings, 


Lr 


Fig.  382.     Clamp  Strap 


MACHINE  SHOP  WORK 


325 


holding  screws,  or  other  projecting  parts.     Also  their  bearing  area 
must  be  sufficiently  large  to  prevent  their  slipping  into  the  bolt 


Fig.  383.     Diagrams  Showing  Cams  or  Eccentrics  Used  for  Clamping 
Courtesy  of  "Machinery",  New  York  Citj 


Fig     3S4.     Typical   Bushings:     Upper   Line — Guiding   Lining  Bushings   for   Drill   Jigs;   Lower 

Left — Screw   Bushing   tor   Locating  Work  Central   with   Hole;   Lower  Center — Screw 

Bushing  for  Locating  Round  Work  by  Recesses;  Lower  Right — Floating  Bushing 

Courtesy  of  "Machinery",  New  York  City 

slots  often  found  in  work  tables.     Whenever  possible  the  jig  should 
be  provided  with  four  feet  instead  of  three. 


326 


MACHINE  SHOP  WORK 


TABLE  XIX 
Dimensions  of  Stationary  Drill  Bushings* 


T 

1 

1 

A 

B 

L 

A 

B 

L 

A 

B 

L 

A 

B 

L 

1 

A 
A 

3 
f 

f 

A 

ji 

H 

f* 

1] 

1A 

H 
1A 

IA 
H 
1A 

2 

13 
11 
V 

\ 
I 

Itt 

2 
11 

PTI-*  H« 
CO  CO  CO 

i 

i 

5 

g 

l 

1  i 

if 

23 

It 

2i 

2- 

f 

I  "J 

P 

A 

f 

7 
I 
1 

;* 

H 

i 

H 

If 

If 

|| 

1 

IH 

if 
iff 

H 

CO  CO  COCO 

ii! 

2 

2f 

27 
1  6 

2| 

tO  bO  bObO 

-'"•Sh"1"^ 

TABLE  XX 
Dimensions  of  Lining  Bushings* 


m    „ 

i 

A 

B 

L 

A 

B 

L 

A 

B 

L 

i 

A 

t 
M 

f 

1 

ii 

ll 

if 

11 

If  - 
If 

H 

H.HSHNHS 
COCO  CO  CO 

2fi 

2f6 

21 

21 

2f 

21 
21 

f 

1 

4 

1  "16 

itt 

2 

2f 

3 

3 

H 

7 
8 

IA 

18 

2| 

29 
16 

3A 

31 

* 

i 

1 

if 

2 

2* 

3j 

M 

if 

H 

if 

24 

1 

2H 
2f 

3f6 

31 
3| 

i 

if 

If 

U 

2f 

2| 

** 

ift 

if 

*Courtesy  of  "Machinery",  New  York  City. 


MACHINE  SHOP  WORK 


327 


TABLE  XXI 
Dimensions  of  Removable  Drill  Bushings* 


— 

'I-  

"1* 

03 

ll 

IM  „, 

1 

*  —  n 

Ml 
• 

ft 

i  — 

A 

B 

C 

D 

E 

F 

H 

I 

K 

i 

f 

i 

1 

f 

f 

| 

| 

A 

i 

A 

I 

i 

31 

.3 
4 

I 

IT 

~r& 

A 

i 

| 

| 

i 

3 
4 

A 

f 

f 

i 

i 

I 

1 

3 

4 

7 
T6 

ji 

i 

i 

1 

I 

A 

i 

i 

u 

1 

2 

A 

t 

i 

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A 

U 

H 
1* 

1 

i 

A 

A 

F 

i 

if 

H 

1 

1A 

1; 

If 

I 
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H 

if 

ll 

1H 

li 

i 

1^ 

A 

7 
8 

H 

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1^ 

1 

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H 

A 

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i 

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i 

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2 

i 

4 

2  • 

U 

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A 

H 

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21 

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21 

2 

A 

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A 

if 

if 
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21 

A 

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2 
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21 

A 

2H 

21 
21 

i 

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if 

2^ 

2J 
21 

2H 

3 

2f 

i 

2A 

1 

if 

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2f 
21 

j 

31 

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s 

2^ 

1ft 

2F 

21 

I 

3i 

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1ft 

3 

f 

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31 

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t 

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2f 

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31 

1 

215 
1  6 

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2ii 

31 

A 

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g  15 

A 

2 

2f 

3^ 

t 

4 

3} 

* 

3^ 

A 

Bushings.  The  soft  body  of  the  jig  cannot  be  used  to 
guide  the  drill  if  much  service  is  required  of  the  jig.  In  all  pro- 
duction work,  the  guide  holes  for  the  drills  are  lined  with  hardened 


*Courtesy  of  "Machinery",  New  York  City. 


328  MACHINE  SHOP  WORK 

TABLE  XXII 
Bushings  for  Holes  Reamed  with  Rose  Chucking  Reamers* 


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tool  steel  bushings,  ground  true  inside  and  out  to  accurate  dimen- 
sions. Fig.  384  illustrates  different  forms  of  guide  bushings  and 
Tables  XIX,  XX,  XXI,  and  XXII  give  accepted  dimensions.  The 
several  types  of  bushings  are  known,  from  their  use  or  by  their 
construction,  as  tight  bushings,  lining  bushings,  slip  bushings,  screw 
bushings,  etc. 

*Courtesy  of  "Machinery",  New  York  City. 


MACHINE  SHOP  WORK  329 

Tolerances.  A  jig  is  usually  a  duplicating  tool  as-  well  as  a 
production  tool.  In  all  machine  work  certain  standards  of  accuracy 
prevail.  Exact  dimensions  are  hard  to  obtain  in  any  work,  and 
certain  commercial  variations  from  the  exact  dimensions  are 
allowable.  Such  variations  from  exactness  of  dimensions  are  known 
as  tolerances.  For  example,  an  allowable  tolerance  of  0.0005  inch 
plus  or  minus  (db)  might  be  used  in  grinding  a  certain  piece  of 
work,  and  all  pieces  ground  would,  if  within  these  limits,  be 
considered  commercially  exact. 

In  jig  construction  certain  tolerances  are  agreed  upon  by  the 
user  of  the  tool,  as  commercially  possible.  The  following  tolerances 
are  from  the  practice  of  the  Taft-Pierce  Company,  and  are  those 
used  for  tool  and  jig  design: 

Information  and  Limits  to  Be  Placed  on  Drawings 

The  following  are  two  important  essentials  that  must  be  carefully  executed 
on  all  drawings  before  the  drawings  are  submitted  to  the  checker  for  his  signature, 
and  are  to  be  considered  as  aids  for  the  better  conception  and  reasoning  of  the 
workman,  in  whose  hands  the  work  is  placed  when  "doping  out"  the  intent 
and  purpose  of  the  drawings. 

Next  to  the  accuracy,  the  efficiency  and  clearness  with  which  these  aids 
are  accomplished  are  of  the  greatest  importance: 

(1)  State  accurately  the  amount  of  limits  of  tolerance  that  may  be  per- 
mitted on  all  dimensions.     (See  sheet  describing  methods  of  expressing  limits.) 

(2)  Issue  with  each  drawing  specifications  written  on  information  blanks 
provided  for  the  purpose,  describing  the  requirements  of  the  drawing  and  giving 
any  information  that  will  be  of  value  to  the  workmen. 

Limits  of  Tolerance  as  Adopted  by  the  Taft-Pierce  Company 

Statement:  If  a  limit  can  be  permitted  above  and  below  the  dimension, 
specify  the  limit  thus:  (±)  giving  the  amount  of  limit  tolerated.  If  a  limit 
can  only  be  permitted  below  the  dimension,  specify  it  thus:  (— )  giving  the 
amount  of  limit  tolerated.  If  a  limit  can  only  be  permitted  above  the  dimension 
specify  it  thus:  (+)  giving  the  amount  of  limit  tolerated. 

Fractions.  Unless  limits  are  specified,  vulgar  fractions  are  capable  in  the 
main  of  a  wide  variation  of  limitation.  For  the  purpose  of  fixing  a  standard, 
however,  it  shall  always  be  understood  that  in  the  event  that  a  fraction  is  not 
accompanied  by  a  limit,  a  minimum  limit  of  (±)  .010  is  permissible.  Fractions 
that  must  be  held  closer  than  this  must  be  accompanied  by  a  specified  amount  of  limit. 

Amounts:  2-Place  Decimals.  If  tolerance  is  not  added,  a  limit  of  (db) 
.005  is  permissible. 

3-Place  and  4-Place  Decimals.  A  3-  or  4-place  decimal  should  be  used 
only  when  absolutely  necessary.  If  tolerance  is  not  added,  a  limit  of  (±)  .0015 
is  permissible. 


330 


MACHINE  SHOP  WORK 


3-Place  and  4-Place  Decimals.     Whenever  through  necessity  three  or  four 
places  must  be  accurately  obtained,  the  dimension  shall  be  marked  EXACT. 

Guide  Bushings.     Locating  the  Guide  Bushings.    While  there 
are  a  great  variety  of  methods  used  when  locating  the  centers  of  the 

holes,  if  exactness  is  desired, 
the  located  centers  are  usually 
positioned  by  making  use  of 
the  jig  buttons  shown  in 
Fig.  385.  These  are  hardened 
and  ground  tool  steel  cylin- 
ders with  the  ends  ground 
parallel.  In  use  the  center 
distances,  called  for  on  the 


Fig.  385. 


Tool-Maker's  Bx 
Washers  fc 


ns  with  Screws  and 
Work 


drawing  of  tJ*e"  jigged  piece,  are  located  approximately  in  position 
on  the  fa^e  of  the  jig.  Each  button  as  purchased  is  furnished 
with  a  clamping  screw  whose  body  fits  loosely  in  the  axial  hole 
in  the  button.  Figs.  386  and  387  show  how  the  buttons  may  be 


Fig.  386.     Positioning  Buttons  with  Micrometer  Caliper 

accurately  positioned  using  precision  tools.  It  will  be  noted  that 
in  each  case  shown  the  buttons  are  first  positioned  by  lightly 
clamping  them  to  an  approximately  accurate  layout,  and  after- 
ward bringing  them  to  accurate  position  by  measurements  made 
with  precision  tools. 


MACHINE  SHOP  WORK 


331 


Boring  Hole  for  Guide  Bushings.  Fig.  388  shows  the  hole  being 
bored.  Previous  to  the  boring,  the  plate  is  clamped  to  a  lathe  face- 
plate and  shifted  to  a  posi- 
tion where  the  accurately 
positioned  button  will  indi- 
cate true  with  the  feeler  of 
a  good  indicator  placed 
against  its  surface.  When 
the  button  rotates  true,  it 
is  removed,  the  hole  is 
roughly  drilled,  afterward 
accurately  bored,  as  shown 
in  the  cut,  and  the  hard- 
ened and  ground  tool  steel 
bushings  pressed  into  place. 
Operating  the  Jig.  If 
the  jig  is  of  a  proper  design 
and  construction,  the  oper- 
-ator  should  have  little 
trouble  in  its  use.  All 
locating  points  and  surf  aces 

Fig.  387.     Positioning  Buttons  with  Vernier  Caliper         snOuld     be     plainly     visible, 


Fig.  388.     Boring  Hole  for  Guide  Bushing 


332 


MACHINE  SHOP  WORK 


the  work  should  go  into  the  jig  only  when  properly  positioned  and 
the  clamping  done  with  despatch,  the  various  tools  should  spindle 
as  shown  in  Fig.  349,  and  the  operator  should  handily  use  each 
spindle  in  logical  order.  The  jig  is  then  discharged  and  newly 
recharged. 

Spotting.     Hand  scraped  or  other  plane  surfaces  are  given  an 
attractive  appearance  by  what  is  termed   "spotting".     A  skilful 


Fig.  389.     Typical  "Spotting"  Pattern  on  Surface  Plate 

worker  with  the  hand  scraper  will  cover  a  plane  surface  with 
regular  spots  in  an  artistic  manner.  Fig.  389  shows  sections  so 
treated.  If  the  spots  are  small  rectangles,  the  result  is  termed 
"snow  flaking".  Another  method  of  handling  the  scraper  results  in 
small  crescents  or  "half  moons",  this  result  is  known  as  "frosting". 
In  all  cases  where  work  is  spotted,  it  results  in  a  pleasing  effect, 
and  adds  to  the  "classiness"  of  the  machine  or  jig.  The  scraping 
pattern  has  also  the  effect  of  making  the  workman  more  careful 
of  such  surfaces. 


MACHINE  SHOP  WORK 


333 


Fixtures 

Importance.  When  work-holding  devices  are  used  in  machine 
practice  they  are  ordinarily  termed  fixtures.  That  these  are 
important  adjuncts  of  the  modern  machine  tool  is  made  evident 


Fig.  390.     Typical  Milling  Fixture 


by  a  study  of  the  various 
production  illustrations 
in  this  book.  For  exam- 
ple, take  the  milling  jobs 
shown,  and  it  at  once 
becomes  apparent  that 
the  fixtures  are  a  prin- 
cipal item  in  the  produc- 
tion figures  given,  and  so 
on  through  the  whole  list 
of  production  machines. 
Milling  Fixtures. 
While  in  some  cases  fix- 
tures can  be  used  inter- 
changeably upon  planers, 
shapers,  boring  mills,  and 
milling  machines,  it  is 


Fig.  391.     Typical  Boring  Fixture 


334 


MACHINE  SHOP  WORK 


more  usual  to  find  them  designed  for  the  particular  machine  on 
which  they  are  to  be  used.  In  Fig.  390  is  shown  a  milling 
machine  fixture  of  a  simple  form  and  construction  designed 
to  hold  the  base  of  a  small  bench  grinder,  while  the  upper  surfaces 
of  the  bearing  boxes  are  being  machined.  This  is  done  with  the 
gang  of  cutters  shown  in  the  illustration.  Such  fixtures  as  this 
cost  little  and  can  be  used  by  inexperienced  employes.  The  increased 


Fig..  392.     Typical  Planer  Fixture,  Showing  Set-Up  for  Planing  Twenty  Square 

Tables  at  One  Setting 
Courtesy  of  Worcester  Polytechnic  Institute  Shops,  Worcester,  Massachusetts 

production  alone,  made  possible  by  even  so  simple  a  fixture  as  the 
one  shown,  warrants  its  construction. 

Boring  Fixtures.  Fig.  391  shows  a  fixture  used  in  boring  out 
the  head  casting  of  a  ball-bearing  lathe.  In  this  fixture,  the  casting 
is  held  while  being  bored.  As  the  spindle  holes  are  located  by  the 
bushed  holes  for  the  boring  bar,  it  is  perhaps  more  of  a  "jig"  than 
a  "fixture".  However,  its  use  is  evident  from  the  cut. 

Planer  Fixtures.  Planer  fixtures  are  usually  simpler  in  design 
and  construction  than  those  in  use  on  either  the  boring  or  the  milling 


MACHINE  SHOP  WORK 


335 


machine.  Fig.  392  is  illustrative  of  the  simplicity  of  planer  fixtures. 
The  cut  shows  it  as  made  for  holding  a  string  of  square  tables  such 
as  are  used  en  sensitive  drillers.  As  shown  in  the  illustration,  a 
double  string  of  tables  are  mounted  and  both  of  the  tool  heads 
are  used. 

BALL  BEARINGS 

Uses  cf  Ball  Bearings.    The  claims  made  for  the  use  of  ball 
bearings  in  preference  to  plain  bearings  are  several  in  number  as 


Fig.  393.     Auburn  Self-Contained  Ball  Thrust  Bearing 
Courtesy  of  Auburn  Ball  Bearing  Company,  Rochester,  New  York 

follows:  Less  wear,  less  frictional  resistance,  more  compact,  non- 
heating  in  use,  less  fitting  than  plain  bearings,  better  shaft  alignment. 
Until  recently  very  little  reliable  information  could  be  obtained 
relative  to  ball  bearings  and  today  it  is  probable  that  their  use  on 
machine  tools  is  much  less 
than  it  should  be.  Their 
extended  use  on  motor  cars 
and  bicycles  has  shown  defi- 
nitely just  what  their  value 
is  in  such  lines,  but  machine 
tool  builders  have  probably 
been  ultra-conservative  in 
their  use.  In  the  high-  speed 

drilling  machines,  their   USe        Fig.  394.     Hess-Bright  Thrust  Bearing  with  a  Lining 

Washer  and  Enclosing  Case 

has   been  remarkably  suc- 
cessful.    Any  of  the  reliable  manufacturers  of  such  bearings  will 
furnish  performance  figures  showing  the  possibilities  of  their  use* 


336 


MACHINE  SHOP  WORK 


•i 


Types  of  Bearings.  Ball  bearings  are  known  generally  under 
two  headings:  "Radial"  and  "Thrust".  In  the  radial  bearing, 
the  load -pressure  is  at  right  angles  or  normal  to  the  shaft  axis,  while 
in  the  thrust  bearing  the  load  pressure  is  parallel 
to  the  axis,  or,  in  other  words,  the  pressure  is  axial. 

Fig.  393  is  representative  of  the  usual  thrust 
bearing,  while  Fig.  394  illustrates  diagrammatically 
the  Hess-Bright  thrust  bearing  with  ball  separating 
retainers. 

Figs.  395  and  396  are  representative  of  the  best 
type  of  radial  ball  bearings.  Radial  ball  bearings 
are  made  in  what  is  known  as  the  single  type  and 
the  double  type.  In  other  words,  bearings  may 
be  obtained  with  either  a  single  row  or  race  of  balls, 
or  they  may  be  obtained  with  two  rows  of  balls. 
While  radial  bearings  are  not  generally  supposed 
to  take  an  axial  load  or  thrust,  many  of  the  better 
radial  types  will  allow  a  certain  amount  of  axial 
thrust  under  favorable  conditions. 

Load  Capacities.  Tables  XXIII  and  XXIV 
give  load  carrying  capacities  of  radial  and  of  axial 
ball  bearings  used  under  light,  medium,  and  heavy 
loading. 

Lubrication.  While  it  was  at  one  time  thought 
odiai  Bali  Bearing  that  ball  bearings  needed  no  lubrication,  this  was 


Tig.  396.     S.  K.  F.  Radial  Bearing  Showing  Parts  and  Assembled  Bearing  Complete 


MACHINE  SHOP  WORK 


337 


TABLE  XXIII 
Load  Capacities  of  Radial  Ball  Bearings* 


DIAMETER 
BORE 

OUTSIDE 
DIAMETER 

WIDTH 

REVOLUTIONS  PER  MINUTE 

300 

600 

1200 

2400 

£!L   i-*- 

Milli- 
meters 

Inches 

Milli- 
meters 

Inches 

Maximum  Load,  Pounds 

EXTRA  HEAVY  TYPE 

17 

0.6693 

62 

2.4409 

20 

0.7874 

1,100 

880 

680 

540 

20 

0  .  7874 

72 

2.8346 

23 

0.9055 

1,450 

1,150 

860 

710 

25 

0.9843 

80 

3  .  1496 

25 

0.9843 

2,000 

1,600 

1,200 

980 

30 

1.1811 

90 

3.5433 

28 

1  .  1024 

2,400 

1,925 

1,450 

1,175 

35 

1.37SO 

100 

3.9370 

30 

1.1811 

2,850 

2,290 

1,700 

1,400 

40 

1  .  5748 

110 

4.3307 

33 

1.2992 

3,300 

2,650 

2,000 

1,650 

45 

1.7717 

120 

4  .  7244 

35 

1.3780 

3,850 

3,075 

2,400 

1,890 

50 

1.9685 

130 

5.1181 

37 

1.4567 

4,400 

3,500 

2,650 

2,150 

55 

2.1651 

140 

5.5118 

40 

1.5748 

5,100 

4,075 

3,100 

2,500 

60 

2.3622 

150 

5.9055 

42 

1.6536 

5,700 

4,560 

3,500 

2,800 

65 

2.5591 

160 

6.2992 

45 

1.7717 

6,800 

5,450 

4,200 

3,350 

70 

2  .  7559 

180 

7.0866 

50 

1.9685 

8,000 

6,400 

4,850 

3,925 

75 

2.9528 

190 

7.4803 

53 

2.0867 

9,200 

7,350 

5,500 

4,500 

80 

3.1496 

200 

7  .  8740 

57 

2.2441 

10,600 

8,500 

6,400 

5,200 

85 

3.3465 

210 

8.2677 

60 

2.3622 

12,000 

9,600 

7,300 

5,900 

90 

3.5433 

225 

8.8583 

63 

2.4803 

13,600 

10,900 

8,200 

6,650 

95 

3  .  7402 

250 

9.8425 

67 

2.6378 

15,400 

12,250 

9,200 

7,550 

100 

3.9370 

205 

10.4331 

70 

2.7559 

17,400 

13,900 

10,400 

8,65  J 

HEAVY  TYPE 

17 

0.669 

62 

2.441 

17 

0.669 

750 

600 

450 

370 

20 

0.787 

72 

2.835 

19 

0.748 

1,000 

800 

600 

490 

25 

0.98* 

80 

3.150 

21 

0.827 

1,200 

960 

750 

590 

30 

1.181 

90 

3.543 

23 

0.905 

1,6.50 

1,325 

920 

810 

.     35 

1.378 

100 

3.937 

25 

0.984 

1,850 

1,475 

1,100 

910 

40 

1.575 

110 

4.331 

27 

1.063 

2,200 

1,750 

1,300 

1,075 

45 

1.772 

120 

4.724 

29 

1.142 

3,000 

2,400 

1,750 

1,475 

50 

1.968 

130 

5   118 

31 

1.220 

3,400 

2,725 

2,100 

1,675 

55 

2.165 

140 

5.512 

33 

1.299 

4,000 

3,200 

2,400 

1,950 

60 

2.362 

150 

5.905 

35 

1.378 

4,400 

3,525 

2,650 

2,150 

65 

2.559 

160 

6.299 

37 

1.457 

5,100 

4,100 

3,100 

2,500 

70 

2.756 

180 

7.087 

42 

1.654 

5,700 

4,550 

3,500 

2,800 

75 

2.953 

190 

7.480 

45 

1.772 

7,000 

5,600 

4,200 

3,400 

80 

3.150 

200 

7.874 

48 

1.890 

8,600 

6,875 

5,100 

4,200 

85 

3.346 

210 

8.268 

52 

2.047 

9,200 

7,350 

5,500 

4,500 

90 

3.543 

225 

8.858 

54 

2.126 

10..000 

8,000 

6,200 

4,900 

95 

3.740 

250 

9.842 

55 

2  .  165 

12,000 

9,600 

7,000 

5,900 

100 

3.937 

265 

10  .  433 

60 

2.362 

13,900 

11,100 

8,400 

6,800 

*  S.  K.  F  Ball  Bearing  Company. 

an  absurd  attitude  and  ball  bearings  are  now  greased  in  some  way. 
Whatever  the  oil  or  grease  used,  it  must  be  such  as  will  prevent  rust 
and  be  free  from  any  acid  or  alkali  likely  to  attack  the  surfaces  of 
the  balls  or  the  ball  races.  A  good  oil  or  grease  is  one  that  keeps 
the  surfaces  bright  and  brilliant  after  months  of  use,  and  besides 
furnishes  the  desired  lubrication.  Vaseline,  vaseline  oilt  or  mineral 


338 


MACHINE  SHOP  WORK 


TABLE  XXIII— (Continued) 
Load  Capacities  of  Radial  Ball  Bearings 


DIAMETER 
BORE 

OUTSIDE 
DIAMETER 

WIDTH 

REVOLUTIONS  PER  MINUTE 

300 

600 

1200 

2400 

*"£;        Inches 

Milli- 
meters 

Inches 

Milli- 
meters 

Inches 

Maximum  Load,  Pounds 

MEDIUM  TYPE 

10 

O.H93 

35 

1.378 

11 

0.433 

290 

230 

175 

140 

12 

0.472 

37 

1.456 

12 

0.472 

330 

265 

200 

165 

15 

0.590 

42 

1.653 

13 

0.511 

375 

300 

220 

185 

17 

0.669 

47 

1.850 

14 

0.551 

490 

390 

290 

240 

20 

0.787 

52 

2.047 

15 

0.590 

600 

480 

360 

295 

25 

0.984 

62 

2.440 

17 

0.669 

880 

705 

530 

430 

30 

.181 

72 

2.834 

19 

0.748 

1,100 

880 

660 

540 

35 

.378 

80 

3  .  149 

21 

0.826 

1,400 

1,125 

840 

685 

40 

.574 

90 

3.543 

23 

0.905 

1,650 

1,325 

990 

800 

45 

.771 

100 

3.937 

25 

0.984 

2,200 

1,760 

1,300 

1,100 

50 

.968 

110 

4.330 

27 

1.063 

2,750 

2,200 

1,650 

1,350 

55 

2.165 

120 

4.724 

29 

1.141 

3,300 

2,650 

2,000 

1,600 

60 

2.362 

130 

5.118 

31 

.220 

3,850 

3,100 

2,300 

1,850 

65 

2.559 

140 

5.511 

33 

.299 

4,200 

3,350 

2,550 

2,050 

70 

2.755 

150 

5.905 

35 

.378 

4,500 

3,600 

2,750 

2,200 

75 

2.952 

160 

6.299 

37 

.456 

5,300 

4,250 

3,100 

2,600 

80 

3.149 

170 

6.692 

39 

.535 

6,000 

4,800 

3,500 

2,950 

85 

3.346 

180 

7.086 

41 

.614 

7,500 

6,000 

4,400 

3,700 

90 

3.543 

190 

7.480 

43 

.692 

8,400 

6,700 

5,100 

4,125 

100 

3.937 

215 

8.464 

47 

.850 

10,400 

8,325 

6,200 

5,100 

110 

4.330 

240 

9.448 

50 

.968 

13,200 

10,500 

7,900 

6,500 

LIGHT  TYPE 

10 

0.393 

30 

.181 

9 

0.354 

220 

175 

120 

108 

12 

0.472 

32 

.259 

10 

0.393 

240 

195 

140 

115 

15 

0.590 

35 

.378 

11 

0.433 

290 

230 

175 

140 

17 

0.669 

40 

.574 

12 

0.472 

350 

280 

210 

170 

20 

0.787 

47 

.850 

14 

0.551 

440 

350 

260 

215 

25 

0.984 

52 

2.047 

15 

0.590 

530 

425 

310 

260 

30 

1.181 

62 

2.440 

16 

0.629 

820 

655 

4  SO 

400 

35 

1.378 

72 

2.834 

17 

0.669 

880 

780 

530 

430 

4(5 

1.574 

80 

3.149 

18 

0.708 

1,200 

960 

700 

590 

45 

1.771 

85 

3.346 

19 

0  .  74S 

1,450 

1,150 

860 

710 

50 

1.968 

90 

3.543 

20 

0.787 

1,650 

1,350 

970 

810 

55 

2.165 

100 

3.937 

21 

0.826 

1,800 

1,450 

1,100 

880 

60 

2.362 

110 

4.330 

22 

0.866 

2,200 

1,750 

1,300 

1,080 

65 

2.559 

120 

4.724 

23 

0.905 

2,550 

2,050 

1,550 

1,250 

70 

2.755 

125 

4.921 

24 

0.944 

2,750 

2,200 

1,650 

1,350 

75 

2.952 

130 

5.118 

25 

0.984 

3,100 

2,480 

1,850 

1,520 

80 

3.149 

140 

5.511 

26 

1.023 

3,750 

3,000 

2,200 

1,835 

85 
90 

3.346 
3.543 

150 
160 

5.905 
6.299 

28 
30    - 

1.102 
1.181 

4,000 
4,400 

3,200 
3,520 

2,400 
2,650 

1,960 
2,150 

100 

3.937 

180 

7.086 

34 

1.338 

5,700 

4,560 

3,500 

2,830 

110 

4.330 

200 

7.874 

3S 

1.496 

7,500 

6,000 

4,400 

3,650 

oil,  are  each  good  for  the  purpose.  Usually  these  are  combined 
in  quantities  to  give  the  desired  consistency  for  the  speed  at  which 
the  bearing  is  rotated. 


MACHINE  SHOP  WORK 


339 


TABLE  XXIV 
Loads  for  Thrust  Collar  Bearings* 


No. 

SIZE 

.    REVOLUTIONS  PER  MINUTE 

OF 

BALLS 

OF 

BALLS 

1500 

1000         500 

300 

'150 

100 

50 

25            10 

MEDIUM  WEIGHT,  LOAD  IN  POUNDS 

8 

i 

145 

190 

245 

285 

333 

395 

540 

660 

1,100 

10 

i 

185- 

245 

310 

365 

430 

505 

660 

825 

1,320 

13 

\ 

240 

320 

395 

485 

550 

650 

870 

1,080 

1,760 

16 

i 

295 

395 

495 

585 

680 

770 

1,045 

1,355 

2,200 

18 

i 

330 

440 

550 

660 

770 

880 

1,175 

1,520 

2,420 

17 

156 

440 

550 

660 

880 

990 

1,285 

1,725 

2,245 

3,300 

18 

ft 

550 

660 

770 

990 

1,210 

1,395 

1,905 

2,400 

3,520 

17 

660 

770 

880 

1,210 

1,540 

1,890 

2,585 

3,255 

4,620 

19 

f 

770 

880 

1,100 

1,430 

1,760 

2,110 

2,880 

3,650 

5,060 

18 

iV 

880 

1,100 

1,320 

1,650 

2,200 

2,465 

3,255 

4,355 

6,380 

19 
18 
19 

f 

990 
1,210 
1,320 

1,210 
1,430 
1,540 

1,540 
1,760 
1,980 

1,870 
2,200 
2,420 

2,420 
2,640 
3,080 

2,605 
3,235 
3,300 

3,430 
4,235 
4,335 

4,620 
5,720 
6,070 

6,820 
8,360 
8,800 

20 

i 

1,430 

1,650 

2,090 

2,530' 

3,300 

3,485 

4,555 

6,380 

9,240 

19 

IV 

1,540 

1,760 

2,420 

2,640 

3,740 

4,180 

•5,455 

8,790 

11,000 

19 

1 

1,870 

2,090 

2,860 

3,300 

4,400 

4,950 

6,600 

9,295 

13,200 

20 

I 

1,980 

2,200 

2,970 

3,520 

4,620 

5,225 

6,950 

9,790 

13,860 

19 

-i 

2,200 

2,530 

3,520 

4,180 

5,280 

5,995 

7,965 

11,255 

15,400 

20 

i 

2,420 

2,640 

3,740 

4,400 

5,500 

6,510 

8,745 

11,440 

16,280 

19 

2,640 

3,080 

3,960 

4,840 

5,940 

7,370 

9,845 

12,640 

17,600 

19 

I 

2,860 

3,520 

4,840 

5,500 

7,040 

8,635 

11,605 

14,830 

22,000 

19 

i 

3,080 

4,180 

5,280 

6,380 

8,140 

10,340 

13,970 

17,600 

24,200 

13 

1 

3,740 

4,840 

6,600 

8,140 

10,560 

13,510 

18,215   I  23,010 

28,600 

LIGHT  WEIGHT,  LOAD  IN  POUNDS 

21 

A 

640 

770 

900 

1,155 

1,410 

1,630 

2,200 

2,970 

4,180 

23 

X 

705 

860 

990 

1,265 

1,540 

1,760 

2,420 

3,255 

4,620 

21 

1 

860 

990 

1,210 

1,595 

1,980 

2,245 

3,035 

4,005 

5,500 

22 

I 

905 

1,045 

1,265 

1,675 

2,090 

2,355 

3,170 

4,180 

5,940 

21 

1,100 

1,320 

1,705 

2,090 

2,530 

2,970 

4,025 

5,280 

7,480 

22 

jg. 

1,155 

1,385 

1,785 

2,200 

2,775 

3,125 

4,225 

5,500 

7,920 

23 

•rs 

1,210 

1,455 

1,870 

2,310 

2,860 

3,255 

4,400 

5,785 

8,140 

25 

A 

1,320 

1,585 

2,035 

2,530 

3,080 

3,520 

4,775 

6,270 

9,020 

27 

A 

1,430 

1,715 

2,200 

2,750 

3,300 

3,830 

5,170 

6,765 

9,680 

28 

5 

1,485 

1,785 

2,310 

2,860 

3,410 

3,960 

5,370 

7,040 

10,120 

29 

"nr 

1,540 

1,850 

2,420 

2,970 

3,520 

4,115 

5,545 

7,260 

10,340 

30 

ft 

1,595 

1,915 

2,530 

3,080 

3,630 

4,270 

5,720 

7,525 

10,780 

*  The  Hess-Brisht  Manufacturing  Company. 

MAGNETIC  CHUCKS 

Uses  in  Production  Work.  A  magnetic  chuck  is  essentially 
an  electromagnet  provided  with  a  flat  work  face.  Fig.  397  shows 
a  magnetic  chuck  of  the  type  commonly  used  on  planers,  milling 
machines,  boring  mills,  and  other  'machines  producing  plane  sur- 
faces. Fig.  398  shows  how  the  magnetic  chuck  is  adapted  to  a  rotat- 
ing spindle.  Each  of  these  tools  are  of  the  greatest  service  in  machin- 
ing small  and  rather  thin  pieces,  as  magnetic  holding  leaves  the  work 
surface  clear  for  tooling. 

The  magnetic  chuck  shown  in  Fig.  397  is  really  two  standard 


340 


MACHINE  SHOP  WORK 


style   1 0-inch  X  32-inch  Heald  magnetic  chucks,   butted  together 
end  to  end,  used  on  a  surface  grinding  machine.    In  the  illustration 


I 


528  cones  are  in  position.    Time  for  placing  does  not  exceed  twelve 
minutes.    The  cones  are  end  ground  to  a  limit  of  0.002  inch. 


MACHINE  SHOP  WORK 


341 


The  total  time  for  the  job  from  start  to  finish  is  If  hours. 
Such  a  job  illustrates  the  usefulness  of  the  magnetic  chuck  upon 
a  surface  grinding  machine.  The  results  are  similar  when  used 
upon  the  milling  machine  and  for  certain  planer  work. 


Fig.  398.     Heald  Internal  Grinder  Fitted  with  Magnetic  Chuck 
Courtesy  of  Heald  Machine  Company,  Worcester,  Massachusetts 

Fig.  398  shows  the  possibilities  of  a  rotary  magnetic  chuck 
used  in  the  grinding  of  holes,  while  Fig.  399  is  illustrative  of  its 
use  in  lathe  work.  The  essential  quality  of  magnetic  chucks  is  that 
the  holding  power  is  exerted  upon  the  work  without  material  straps, 
bolts,  or  other  devices,  which  of  themselves  take  up  space  and  may 


342 


MACHINE  SHOP  WORK 


Fig.  399.     Close  View  of  Heald  Chuck  Holding  Disc  for  Turning  Operation 

interfere  with  the  tooling  which  needs  to  be  accomplished.    Also 
they  are  instantaneously  discharged  by  pulling  a  simple  switch. 


Fig.  400.     View  of  Magnetic  Chuck  Casting 

and  Unit  Coils 

Courtesy  of  Heald  Machine  Company, 
Worcester,  Massachusetts 

The  diagram,  Fig.  400,  illustrates  the  simple  construction  oi 
the  magnetic  chuck. 


MACHINE  SHOP  WORK 


343 


Fig.  401.    Heald  Magnetic  Chuck  Faceplate 


SAFETY  FIRST 

A  growing  apprehension  of  the  possibilities  of  so  safeguarding 
machines  that  the  operator  is  reasonably  sure  that  he  incurs  little 
risk  of  life  or  limb,  would  seem  to  render  timely  a  few  words  on  this 
subject. 

Safety  Devices  on  Machines.  It  is  well  perhaps  to  note  that  no 
machine  can  be  absolutely  safeguarded  and  be  operative.  The 
danger  to  the  operator  can,  however,  with  care,  be  reduced  to  a 
minimum,  and  much  is  now  being  done  to  safeguard  such  portions 
of  machine  tools  as  the  gearing,  the  clutches,  clutch  couplings, 
belts,  set  screws,  etc. 

While  the  whole  subject  of  "safety  first"  includes  the  building 
in  which  the  machines  are  located,  as  well  as  the  machines  themselves, 
in  general  the  machines  should  receive  the  first  consideration.  It 
is  the  truth  that  nothing  can  safeguard  a  machine  against  ignorance, 
bravado,  or  heedlessness  on  the  part  of  the  operative,  and  he  must 
either  educate  himself  or  be  educated  to  a  point  where  he  will  vol- 
untarily endeavor  to  protect  himself  against  injury. 

While  it  is  usually  true  that  the  employe  has  very  little  direct 
authority  in  the  matter  of  providing  safeguards  for  the  machines 
at  which  he  may  work,  also  in  regard  to  the  building  in  which  he 
works,  he  may,  by  means  of  tactful  suggestions  made  to  the  proper 
person,  do  much  indirectly  to  promote  the  cause  of  safety.  While 
usually  the  building  in  which  the  machinery  is  located  must  be 
taken  as  it  is,  many  improvements  can  be  made  with  safety  first 
in  view. 


344  MACHINE  SHOP  WORK 

Means  of  Safeguarding.  Fire  Hazard.  One  of  the  common 
hazards  is  the  danger  of  fire.  This  is  a  real  danger  to  the  employes' 
life  if  the  building  exceeds  the  height  of  a  single  story;  and  properly 
guarded  stairways  and  fire  escapes  should  provide  easy  exit.  All 
exits  should  be  designated  by  the  word  EXIT  in  prominent  char- 
acters and  all  doors  should  open  outward.  Unobstructed  passage 
to  any  and  all  exits  should  be  maintained  at  all  times,  and  all  stair- 
ways should  preferably  be  of  a  generous  width  and  without  bends 
or  crooks.  All  stairways  or  other  floor  openings,  as  for  example, 
elevator  wells,  should  be  safeguarded  by  suitable  railings  or  nettings. 

Power  Transmission.  The  transmission  of  power  by  means 
of  shafting,  pulleys,  and  belting,  is  a  prominent  hazard  to  safety 
unless  it  is  properly  safeguarded.  Power  driven  gears,  pulleys, 
and  flywheels  should  be  encased  to  at  least  6  feet  from  the  floor. 
All  chain  drives  should  be  entirely  encased,  as  should  trains  of 
gearing.  Belts  should  be  guarded  to  a  height  of  at  least  6  feet 
from  the  floor  or  any  adjacent  platform. 

Shafting.  All  line  shafting,  even  if,  as  is  usually  the  case, 
it  is  suspended  from  the  ceiling,  should  be  provided  with  necessary 
safeguards,  as  for  example,  smooth  couplings,  flush  set  screws, 
proper  provision  for  belts  when  not  on  the  pulleys,  etc. 

Electrical  Transmission.  All  switchboards  should  stand  out 
from  the  wall  to  have  a  free  and  clear  space  sufficient  for  easy  and 
safe  inspection.  This  space  should  be  enclosed  with  provision  for 
padlocked  entrances  and  exits.  It  should  have  also  a  prominent 
sign  DANGER. 

Wherever  it  is  possible  for  the  operative  to  accidentally  make 
a  dangerous  ground  connection,  rubber  matting  should  be  provided 
and  kept  in  a  dry  condition.  High  voltage  lines  should  have  prom- 
inently attached  red  signs  stating  the  voltage.  All  switches  should 
be  guarded  from  accidental  contacts. 

Machinery.  All  those  machines  which  receive  their  power 
through  a  system  of  gearing,  screws,  spindles,  pulleys,  etc.,  should 
have  all  the  working  mechanisms  covered.  It  will  be  noted  that  in 
essentially  all  of  the  production  machines  shown  in  this  course, 
all  moving  parts  have  been  encased  wherever  it  was  possible  to 
do  so  without  interfering  with  the  convenient  operation  of  the 
machine. 


MACHINE  SHOP  WORK  345 

Woodworking  Machinery.  This  is  a  very  dangerous  class  of 
machinery  and  should  receive  special  care  in  providing  guards. 
The  floor  adjacent  to  such  machinery  as  this  should,  as  in  the  case 
of  electrical  apparatus,  be  covered  with  rubber  matting. 

Grinding  Machines.  Owing  to  the  high  rotative  speed  given  to 
abrasive  wheels  in  modern  grinding,  especial  precautions  should 
also  be  made  to  safeguard  the  workmen  from  a  possible  wheel 
explosion.  While  the  manufacturer  is  painstaking  in  his  efforts 
to  safeguard  his  machines,  it  is  not  possible  for  him  to  prevent 
an  ignorant  or  careless  operative  from  rendering  such  safeguards 
inoperative. 

Use  of  Goggles.  In  all  operations  which  result  in  flying  chips, 
the  use  of  goggles  is  recommended.  This  includes  such  operations 
as  snagging,  chipping,  hand  grinding,  and  many  other  jobs. 

Press  Work.  All  machines  for  punching,  shearing,  or  pressing 
metals  or  other  materials  should,  in  addition  to  the  ordinary  safe- 
guards, be  provided  with  special  safeguards  at  the  working  opening. 
These  should  absolutely  prevent  the  closing  of  the  machine  while 
the  operatives'  hands  are  exposed  to  injury. 

In  General.  The  art  of  safeguarding  the  workman  is  one  that 
requires  thought,  ingenuity,  and  an  unwillingness  to  ignore  any 
little  detail  that  will  in  any  way  achieve  the  end  sought — Safety  First, 


INDEX 


INDEX 


Page 
A 

Angle  cutters  139 

Automatic   gear-cutting   machine  224 

Automatic  screw  machines  250 

hollow  mills  262 

setting-up  machine  262 

types  of  251 

Automatic    turning    and    chucking 

machine  252 

Automatics  303 


B 


Ball  bearings  335 

load  capacities  336 

lubrication  336 

types  of  336 

use  of  335 

Becker  gear-cutting  machine  224 

Belting  190 

Bench  gear-cutting  machine  225 

Bench  miller  145 

Bevel  5 

Bevel  gears  206 

Bilgram  gear-planing  machine  227 

Bolt  cutter  52 

Bolt  threads,  cutting  of  51 

Boring  fixtures  334 

Broaching  machines  309 

types  of  and  nature  of  work  309 

Brown  and  Sharpe  automatic  screw 

machine  258 
Brown    and    Sharpe    gear-cutting 

machine  223 


Caliper  square  12 

Calipers  9 

caliper  square  12 

outside  and  inside  9 

transfer  11 

vernier  16 


Cams 

Cape  chisel 
Carpenter's  rule 
Center  punch 
Center  square 
Chisels 

cape 

chipping 

cutting  edge  of 

diamond-point 

flat 

round-nose 

Cleveland  automatic  machine 
Cold  chisels 
Combination  set 
Cutter  arbor 

cutter,  locating  position  of 

fastening  cutter  in  arbor 
Cutting  speeds 
Cutting  speeds  and  feeds 
Cutting  tools 

chisels 

files 

hand  scraping 
Cutters,  lubrication  of 
Cutters,  speed  of 

D 

Diamond  point  chisel 

Die  holders,  threading  of 

Dividers 

Dovetails 

Drillers 

drilling  operation 

flat 

heavy  high-speed 

holding  work 

laying  out 

light  high-speed 

multiple  spindles 

power  feed 


INDEX 


Page 
Drillers  (continued) 

radial  113 

sensitive  110 

special  291 

tapping  118 

Drilling  38 

Drilling  machines  290 

automatics  303 

cutting  speeds  and  feeds  303 

heavy  high-speed  drillers  290 

holding  work  293 

light  high-speed  drillers  291 

lubrication  294,  303 

production  figures  292 

special  drillers  291 

turning  lathe  296 

Drilling  operation  109 

Drills  38 

care  of  41 

lubrication  41 

resharpening  42 

speed  of  41 

farmer  40 

flat  38 

flat  chucking  drill  38 

twist  38 

tapered  shanks  39 

Duplex  milling  machines  152 

E 

End  mills  cutter  142 

dovetail  cutters  >  142 

T-slot  cutter  142 

Engine  lathes  56,  233 

gear  drive  57 

handling  work  59 

tool-feeding  mechanism  59 

spindle  arrangement  57 

Expanding  reamer  and  arbor  45 


Farmer  drills  40 

Feed  221 

Fellows  gear  shaper  225 

Files  28 

characteristics  28 

choice  of  32 

cleaning  32 


Files  (continued) 

convexity  of 

correct  filing  position 

draw  filing 

handles 

height  of  work  for 

polishing 

style  and  cuts 

use  of  powders  and  cloths 
Filing  templets 
Fitting 

Fitting  brasses 
Fixed  gages 
Flat  chisel 

Flat  chucking  ronmer 
Flat  drills 
Flat  square 
Fluting  rollers 
Fluting  taps  and  reamers 
Form  cutters 

G 

Gages 

fixed 

limit 

plug 

ring 

Gang  mills 
Gear  cutting 

tooth  parts,  names  of 

toothed  gearing,  theory  of 
Gear-cutting  machines,  types  of 

automatic 

Becker 

bench 

Bilgram  gear-planing  machine 

Brown  and  Sharpe 

Fellows  gear  shaper 

Gleason  gear  planer 

Whiton 
Gear-cutting  processes 

cutters,  lubrication  of 

cutters,  speed  of 

feed 

gear  teeth,  tools  for  testing 

general  conditions  of 

hobbing  gears 

milling  process 


INDEX 

3 

Page 

Page 

Sear-cutting  processes  (continued) 

Hand-operated  tools  (continued) 

planing  process 

216 

drilling 

38 

spiral 

221 

drills 

38 

ear  teeth,  tools  for  testing 

218 

hammers 

24 

lear-tooth  curves,  development  of 

197 

hand  punches 

36 

rears 

168 

hand  threading  tools 

47 

bevel 

171 

measuring  tools 

1 

dividing  head,  use  of 

169 

reamers 

43 

forms  of  cutters 

168 

templets 

37 

rack  cutting 

171 

Hand  punches 

36 

spiral 

171 

center  punch 

36 

worm 

171 

prickpunch 

36 

ears,  designing 

196 

scratch  awl 

37 

bevel  gears 

206 

Hand  reaming 

44 

diametral  pitch  method 

196 

Hand  scraping 

35 

fixed  pitch  method 

196 

scraping  for  finish  only 

36 

gear-tooth  curves,  development  of 

197 

testing  plane  surfaces 

35 

internal  gears 

203 

Hand  tapping 

48 

spiral  gears 

211 

starting  tap 

49 

teeth  racks 

205 

use  of  bottoming  tap 

49 

worm  gearing 

208 

Hand  threading  tools 

47 

Gears  (internal) 

203 

hand  tapping 

48 

Generating  surface  plates 

184 

lubrication 

49 

jleason  gear  planer 

226 

machine  tapping 

49 

Graver 

55 

sizes  of  drill  for  tapped  hole 

47 

Grinding  machine                             171, 

270 

taps,  types  of 

47 

abrasive  wheels 

273 

threading  dies 

50 

cylindrical  grinding 

271 

Hand  turning,  tools  for 

54 

features  of 

172 

graver 

55 

finishing  to  size  after  caseharden- 

round  nose 

55 

ing 

173 

slide  rest 

56 

grinding  allowances 

273 

Hard  metals,  drilling  of 

183 

•  grinding  methods 

274 

Hobbing  gears 

217 

grinding  wheel,  selecting 

175 

Holes,  laying  out  and  drilling 

162 

lapping 

176 

Horizontal  milling  machines           146, 

285 

lubrication 

175 

backlash  error,  avoiding 

148 

usefulness 

270 

micrometer  graduations 

147 

value  of 

171 

wheel  speed 

271 

I 

wheel  traverse 

272 

Grinding  valves 

184 

Inserted-tooth  cutters 

139 

Grinding  wheel 

175 

Interlocking  .cutters 

139 

juide  bushing 

330 

H 

Jammers 
soft 

24 
25 

J 
Jigs 
Joints 

38 
185 

Eland-operated  tools 

1 

K 

cutting  tools 

25 

Keyseat  rule 

3 

INDEX 


tapping 

Lathe,  layout  for 

Lathes 

engine  lathes 

origin 


tools  for  hand  turning 
Limit  gages 
Lining  shafting 


Page 

176 

181 

53 

56 

53 

53 

54 

20 

188 


Lubrication 


49,  175,  303,  309 


M 


Machine  building  vs.  machine  man- 
ufacturing 265 
Machine  setting  189 
Machine  shop  work                             1-345 
hand-operated  tools  1 
modern  manufacturing  265 
power-driven  tools  53 
shop  suggestions  182 
work,  laying  out  178 
Machine  tapping  49 
Magnetic  chucks  339 
uses  in  production  work  339 
Marking  templets  37 
Measuring  tools  1 
angular  measurement  1 
bevel  5 
center  square  6 
combination  set  6 
flat  square  4 
keyseat  rule  3 
protractor  6 
straightedge  2 
surface  gage  1 
try  square  4 
linear  measurement  6 
calipers  9 
carpenter's  rule  7 
dividers  8 
fixed  gages  18 
micrometers                             •       12 
steel  rule  7 
surface  plates  22 
work  bench  22 
work  vises  23 
Micrometers  12 


Micrometers  (continued) 

reading  of 
Milling  cutters 

angle 

care  of 

characteristics 

classification 

cutter  arbor 

end  mills 

form 

gang  mills 

grinding 

inserted-tooth 

interlocking 

mounting,  methods  of 

plain 

side 

spiral  1 

Milling  fixtures  3. 

Milling  machine  vs.  shaper  and  planer  1J 


Milling  machines 
cutting  feeds 
cutting  speeds 
horizontal 
operations  (simple) 
planer 

production  cutters 
tool  lubrication 
types  of 

bench  miller 

duplex 

horizontal 

plain    and    universal    millers, 
distinction  between 

planer  type 

slabbing  miller 

vertical 
vertical 
work  holding 
Milling  operations 
cams 
classification 

angle  milling 

form  milling 

plane  milling  or  surface  milling  1« 

profiling  1. 

side  milling  or  face  milling          II 
cutting  speeds  1. 


131,  2! 
2 
2 
2 
1 
2 
2 
2 
1 
1 
1 
1 


INDEX 


I;  ing  operations  (continued) 

dovetails 

fluting  taps  and  reamers 

grinding  milling  cutters 

holes,  laying  out  and  drilling 

milling  cutters,  care  of 

milling  machine,  preparing  of 


Page 

163 
164 
154 
162 
154 
156 

oil,  use  of  on  machines  and  work     161 
spirals  165 

splining  shafts  163 

lling  process  214 

>dern  manufacturing  265 

ball  bearings  335 

machine    building    vs.     machine 

manufacturing  265 

magnetic  chucks  339 

production  machines  269 

broaching  machines  309 

drilling  machines  290 

grinding  machines  270 

milling  machines  285 

planing  machines  306 

reduction  methods  266 

automatic  control  267 

automatics  267 

ball  bearings  268 

bearing  alloys  268 

bearing  lubrication  268 

cold  worked  metals  267 

cutting  feeds  266 

cutting  lubrication  266 

cutting  speeds  266 

die  casting  machine  parts  267 

drives  268 

heat  treatment  268 

jigs  and  fixtures  269 

motion  study  269 

overheads  269 

selling  costs  269 

special  die  f  orgings  268 

special  molding  processes  267 

specialized  cutting  steels  266 

single  purpose  machines  266 

time  study  269 

reduction  tools,  jigs,  and  fixtures  314 
afety  first  343 

safeguarding,  means  of  344 

safety  devices  on  machines         343 


Monitor  lathe 
Multiple  spindles 


X 


No.  2  automatic  screw  machine 


O 


Page 
232 
113 


262 


Oil,  use  of  on  machines  and  work  161 


Peening  182 
Pickling  187 
Pipe  threads,  cutting  of  51 
Plain  and  universal  millers,  distinc- 
tion between  149 
Plain  milling  cutters  137 
Plain  shell  reamer  45 
Planer  fixtures  334 
Planer  milling  machine  285 
Planer  tools  121 
Planer  type  milting  machines  150 
milling  attachments  for  150 
Planers  118 
plate  125 
tools  121 
work,  holding  122 
Planing  machines  306 
holding  work  307 
lubrication  309 
production  planers  306 
Planing  process  216 
Plate  planer  125 
Plug  gages  19 
Power-driven  tools  53 
automatic  screw  machines  250 
drillers  109 
gear  cutting  193 
gear-cutting  machines,  types  of        222 
gear  cutting  processes  214 
gears,  designing  196 
grinding  machine  171 
lathe  equipment  60 
lathe  operations  83 
lathes  53 
milling  cutters  133 
milling  machines  131 


INDEX 


Page 
Power-driven  tools  (continued) 

milling  operations  153 

planers  188 

shapers  126 

turret  lathes  229 

Power  feed  driller  111 

Prickpunch  36 

Production  planers  306 

Protractor  6 


R 


Racks,  teeth  of  205 

Radial  driller  113 

universal  114 

Reamers  43 

expanding  45 

hand  reaming  44 

plain  shell  45 

reamer  with  inserted  blades  46 

rose  shell  45 

solid  hand  44 

spiral  chucking  reamer  drill  45 

taper  46 

use  of  43 

Ring  gages  19 

Rose  shell  reamer  45 

Round  bars,  cutting  of  178 

Round-nose  chisel  26 

S 

Scale  187 

Scratch  awl  37 

Sensitive  driller  110 

Shapers  126 

Side  milling  cutters  137 

Slabbing  miller  147 

Slide  rest  56 

Splining  shafts  163 

Slotter  128 

Solid  dies  50 

Solid  hand  reamer  44 

Speed  lathes  53 

Spiral  chucking  reamer  45 

Spiral  cutters  137 

Spiral  gears  211 

cutting  of  221 

Spirals  165 


Split  dies 
Spotting 
Steel  rule 
Straightedge 
Surface  gage 
Surface  plates 


Tables 

allowances  for  grinding  2 

bushings  for  holes  reamed   with 

rose  chucking  reamers     3 
carbon-steel  drills  2 

data  on  rates  of  production  with 
different     types     of 
broaching  machines          3 
dimensions  of  lining  bushings  3 

dimensions  of  removable  .drill 

bushings  3 

dimensions   of  stationary   drill 

bushings  3 

drills,  speed  of 

end  or  face  milling  of  cast  iron  1 
face  milling  of  soft  machinery  steel  I 
high-speed  drills  2 

involute  gear  tooth  parts  2 

load  capacities  of  radial  drill  bear- 
ings 337,  3 
loads  for  thrust  collar  bearings         3 
Norton  grade  list  2 
rate  of  grinding  gun  parts  on  ver- 
tical grinder  2 
revolutions  per  minute  for  various 

sizes  of  grinding  2 

selection  of  grades  278,  2 

speed  of  grinding  wheels  1 

speeds  and  feeds  for  milling  cutters  1 
surface  milling  of  cast  iron  1 

surface  milling  of  soft  machinery 

steel  1 

taps    and    corresponding    drills 
U.  S.  standard  threads,  bolts,  and 

nuts  1 

Taper  reamers 

types  of 

Tapping  I 

Taps 
Templets 


INDEX 


Page 
Templets  (continued) 

filing  38 

jigs  38 

marking  37 

Threading  dies  50 

bolt  threads,  cutting  of  51 

pipe  threads,  cutting  of  51 

solid  dies  50 

split  dies  50 

Tolerances  329 

Toothed  gearing,  theory  of  193 

Try-square  4 

Turning  lathe  296 

Turret-lathe  tools  239 

box  tool  (double)  241 

box  tool  holder  242 

box  tool  (simple)  241 

cross-slide  243 

plain  drill  holder  240 

releasing  holder  241 

split  collet         .  240 

tool  clamp  242 

turret  holder  242 


Turret  lathes 

classification  of 

operations 

original  form  of 

tools 
Twist  drills 


Page 
229 
230 
244 
230 
239 
38 


U 


Universal  multiple-spindle  automatic 

machine  256 


Vernier  calipers 
how  to  read 
Vertical  milling  machines 

W 

Whiton  gear-cutting  machine 
Work  bench 
Work  vises 
Worm  gearing 


16 

17 

151,  285 


222 

22 

23 

208 


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